diff --git a/9-regular-expressions/08-regexp-character-sets-and-ranges/2-find-time-2-formats/solution.md b/9-regular-expressions/08-regexp-character-sets-and-ranges/2-find-time-2-formats/solution.md
index 91568d03..69ade1b1 100644
--- a/9-regular-expressions/08-regexp-character-sets-and-ranges/2-find-time-2-formats/solution.md
+++ b/9-regular-expressions/08-regexp-character-sets-and-ranges/2-find-time-2-formats/solution.md
@@ -1,8 +1,8 @@
 Answer: `pattern:\d\d[-:]\d\d`.
 
 ```js run
-let reg = /\d\d[-:]\d\d/g;
-alert( "Breakfast at 09:00. Dinner at 21-30".match(reg) ); // 09:00, 21-30
+let regexp = /\d\d[-:]\d\d/g;
+alert( "Breakfast at 09:00. Dinner at 21-30".match(regexp) ); // 09:00, 21-30
 ```
 
 Please note that the dash `pattern:'-'` has a special meaning in square brackets, but only between other characters, not when it's in the beginning or at the end, so we don't need to escape it.
diff --git a/9-regular-expressions/08-regexp-character-sets-and-ranges/2-find-time-2-formats/task.md b/9-regular-expressions/08-regexp-character-sets-and-ranges/2-find-time-2-formats/task.md
index 868115bd..c8441caf 100644
--- a/9-regular-expressions/08-regexp-character-sets-and-ranges/2-find-time-2-formats/task.md
+++ b/9-regular-expressions/08-regexp-character-sets-and-ranges/2-find-time-2-formats/task.md
@@ -5,8 +5,8 @@ The time can be in the format `hours:minutes` or `hours-minutes`. Both hours and
 Write a regexp to find time:
 
 ```js
-let reg = /your regexp/g;
-alert( "Breakfast at 09:00. Dinner at 21-30".match(reg) ); // 09:00, 21-30
+let regexp = /your regexp/g;
+alert( "Breakfast at 09:00. Dinner at 21-30".match(regexp) ); // 09:00, 21-30
 ```
 
 P.S. In this task we assume that the time is always correct, there's no need to filter out bad strings like "45:67". Later we'll deal with that too.
diff --git a/9-regular-expressions/08-regexp-character-sets-and-ranges/article.md b/9-regular-expressions/08-regexp-character-sets-and-ranges/article.md
index 6beca62b..cb6a27e9 100644
--- a/9-regular-expressions/08-regexp-character-sets-and-ranges/article.md
+++ b/9-regular-expressions/08-regexp-character-sets-and-ranges/article.md
@@ -130,18 +130,18 @@ In the example below the regexp `pattern:[-().^+]` looks for one of the characte
 
 ```js run
 // No need to escape
-let reg = /[-().^+]/g;
+let regexp = /[-().^+]/g;
 
-alert( "1 + 2 - 3".match(reg) ); // Matches +, -
+alert( "1 + 2 - 3".match(regexp) ); // Matches +, -
 ```
 
 ...But if you decide to escape them "just in case", then there would be no harm:
 
 ```js run
 // Escaped everything
-let reg = /[\-\(\)\.\^\+]/g;
+let regexp = /[\-\(\)\.\^\+]/g;
 
-alert( "1 + 2 - 3".match(reg) ); // also works: +, -
+alert( "1 + 2 - 3".match(regexp) ); // also works: +, -
 ```
 
 ## Ranges and flag "u"
diff --git a/9-regular-expressions/09-regexp-quantifiers/1-find-text-manydots/solution.md b/9-regular-expressions/09-regexp-quantifiers/1-find-text-manydots/solution.md
index d4ddb136..21b8762e 100644
--- a/9-regular-expressions/09-regexp-quantifiers/1-find-text-manydots/solution.md
+++ b/9-regular-expressions/09-regexp-quantifiers/1-find-text-manydots/solution.md
@@ -2,8 +2,8 @@
 Solution:
 
 ```js run
-let reg = /\.{3,}/g;
-alert( "Hello!... How goes?.....".match(reg) ); // ..., .....
+let regexp = /\.{3,}/g;
+alert( "Hello!... How goes?.....".match(regexp) ); // ..., .....
 ```
 
 Please note that the dot is a special character, so we have to escape it and insert as `\.`.
diff --git a/9-regular-expressions/09-regexp-quantifiers/1-find-text-manydots/task.md b/9-regular-expressions/09-regexp-quantifiers/1-find-text-manydots/task.md
index 6fd91bdc..4140b4a9 100644
--- a/9-regular-expressions/09-regexp-quantifiers/1-find-text-manydots/task.md
+++ b/9-regular-expressions/09-regexp-quantifiers/1-find-text-manydots/task.md
@@ -9,6 +9,6 @@ Create a regexp to find ellipsis: 3 (or more?) dots in a row.
 Check it:
 
 ```js
-let reg = /your regexp/g;
-alert( "Hello!... How goes?.....".match(reg) ); // ..., .....
+let regexp = /your regexp/g;
+alert( "Hello!... How goes?.....".match(regexp) ); // ..., .....
 ```
diff --git a/9-regular-expressions/09-regexp-quantifiers/2-find-html-colors-6hex/solution.md b/9-regular-expressions/09-regexp-quantifiers/2-find-html-colors-6hex/solution.md
index d4d297a1..b9e1f85a 100644
--- a/9-regular-expressions/09-regexp-quantifiers/2-find-html-colors-6hex/solution.md
+++ b/9-regular-expressions/09-regexp-quantifiers/2-find-html-colors-6hex/solution.md
@@ -7,11 +7,11 @@ Then we can look for 6 of them using the quantifier `pattern:{6}`.
 As a result, we have the regexp: `pattern:/#[a-f0-9]{6}/gi`.
 
 ```js run
-let reg = /#[a-f0-9]{6}/gi;
+let regexp = /#[a-f0-9]{6}/gi;
 
 let str = "color:#121212; background-color:#AA00ef bad-colors:f#fddee #fd2"
 
-alert( str.match(reg) );  // #121212,#AA00ef
+alert( str.match(regexp) );  // #121212,#AA00ef
 ```
 
 The problem is that it finds the color in longer sequences:
diff --git a/9-regular-expressions/09-regexp-quantifiers/2-find-html-colors-6hex/task.md b/9-regular-expressions/09-regexp-quantifiers/2-find-html-colors-6hex/task.md
index 80ed625f..9a1923a7 100644
--- a/9-regular-expressions/09-regexp-quantifiers/2-find-html-colors-6hex/task.md
+++ b/9-regular-expressions/09-regexp-quantifiers/2-find-html-colors-6hex/task.md
@@ -5,11 +5,11 @@ Create a regexp to search HTML-colors written as `#ABCDEF`: first `#` and then 6
 An example of use:
 
 ```js
-let reg = /...your regexp.../
+let regexp = /...your regexp.../
 
 let str = "color:#121212; background-color:#AA00ef bad-colors:f#fddee #fd2 #12345678";
 
-alert( str.match(reg) )  // #121212,#AA00ef
+alert( str.match(regexp) )  // #121212,#AA00ef
 ```
 
 P.S. In this task we do not need other color formats like `#123` or `rgb(1,2,3)` etc.
diff --git a/9-regular-expressions/10-regexp-greedy-and-lazy/3-find-html-comments/solution.md b/9-regular-expressions/10-regexp-greedy-and-lazy/3-find-html-comments/solution.md
index b3290607..0244963d 100644
--- a/9-regular-expressions/10-regexp-greedy-and-lazy/3-find-html-comments/solution.md
+++ b/9-regular-expressions/10-regexp-greedy-and-lazy/3-find-html-comments/solution.md
@@ -5,11 +5,11 @@ An acceptable variant is `pattern:<!--.*?-->` -- the lazy quantifier makes the d
 Otherwise multiline comments won't be found:
 
 ```js run
-let reg = /<!--.*?-->/gs;
+let regexp = /<!--.*?-->/gs;
 
 let str = `... <!-- My -- comment
  test --> ..  <!----> ..
 `;
 
-alert( str.match(reg) ); // '<!-- My -- comment \n test -->', '<!---->'
+alert( str.match(regexp) ); // '<!-- My -- comment \n test -->', '<!---->'
 ```
diff --git a/9-regular-expressions/10-regexp-greedy-and-lazy/3-find-html-comments/task.md b/9-regular-expressions/10-regexp-greedy-and-lazy/3-find-html-comments/task.md
index 81fd5c63..551d9c72 100644
--- a/9-regular-expressions/10-regexp-greedy-and-lazy/3-find-html-comments/task.md
+++ b/9-regular-expressions/10-regexp-greedy-and-lazy/3-find-html-comments/task.md
@@ -3,11 +3,11 @@
 Find all HTML comments in the text:
 
 ```js
-let reg = /your regexp/g;
+let regexp = /your regexp/g;
 
 let str = `... <!-- My -- comment
  test --> ..  <!----> .. 
 `;
 
-alert( str.match(reg) ); // '<!-- My -- comment \n test -->', '<!---->'
+alert( str.match(regexp) ); // '<!-- My -- comment \n test -->', '<!---->'
 ```
diff --git a/9-regular-expressions/10-regexp-greedy-and-lazy/4-find-html-tags-greedy-lazy/solution.md b/9-regular-expressions/10-regexp-greedy-and-lazy/4-find-html-tags-greedy-lazy/solution.md
index c453926f..b4d9f749 100644
--- a/9-regular-expressions/10-regexp-greedy-and-lazy/4-find-html-tags-greedy-lazy/solution.md
+++ b/9-regular-expressions/10-regexp-greedy-and-lazy/4-find-html-tags-greedy-lazy/solution.md
@@ -2,9 +2,9 @@
 The solution is `pattern:<[^<>]+>`.
 
 ```js run
-let reg = /<[^<>]+>/g;
+let regexp = /<[^<>]+>/g;
 
 let str = '<> <a href="/"> <input type="radio" checked> <b>';
 
-alert( str.match(reg) ); // '<a href="/">', '<input type="radio" checked>', '<b>'
+alert( str.match(regexp) ); // '<a href="/">', '<input type="radio" checked>', '<b>'
 ```
diff --git a/9-regular-expressions/10-regexp-greedy-and-lazy/4-find-html-tags-greedy-lazy/task.md b/9-regular-expressions/10-regexp-greedy-and-lazy/4-find-html-tags-greedy-lazy/task.md
index e3c39c37..8e96c921 100644
--- a/9-regular-expressions/10-regexp-greedy-and-lazy/4-find-html-tags-greedy-lazy/task.md
+++ b/9-regular-expressions/10-regexp-greedy-and-lazy/4-find-html-tags-greedy-lazy/task.md
@@ -5,11 +5,11 @@ Create a regular expression to find all (opening and closing) HTML tags with the
 An example of use:
 
 ```js run
-let reg = /your regexp/g;
+let regexp = /your regexp/g;
 
 let str = '<> <a href="/"> <input type="radio" checked> <b>';
 
-alert( str.match(reg) ); // '<a href="/">', '<input type="radio" checked>', '<b>'
+alert( str.match(regexp) ); // '<a href="/">', '<input type="radio" checked>', '<b>'
 ```
 
 Here we assume that tag attributes may not contain `<` and `>` (inside squotes too), that simplifies things a bit. 
diff --git a/9-regular-expressions/10-regexp-greedy-and-lazy/article.md b/9-regular-expressions/10-regexp-greedy-and-lazy/article.md
index e014c16d..4298e7c8 100644
--- a/9-regular-expressions/10-regexp-greedy-and-lazy/article.md
+++ b/9-regular-expressions/10-regexp-greedy-and-lazy/article.md
@@ -17,11 +17,11 @@ A regular expression like `pattern:/".+"/g` (a quote, then something, then the o
 Let's try it:
 
 ```js run
-let reg = /".+"/g;
+let regexp = /".+"/g;
 
 let str = 'a "witch" and her "broom" is one';
 
-alert( str.match(reg) ); // "witch" and her "broom"
+alert( str.match(regexp) ); // "witch" and her "broom"
 ```
 
 ...We can see that it works not as intended!
@@ -105,11 +105,11 @@ To make things clear: usually a question mark `pattern:?` is a quantifier by its
 The regexp `pattern:/".+?"/g` works as intended: it finds `match:"witch"` and `match:"broom"`:
 
 ```js run
-let reg = /".+?"/g;
+let regexp = /".+?"/g;
 
 let str = 'a "witch" and her "broom" is one';
 
-alert( str.match(reg) ); // witch, broom
+alert( str.match(regexp) ); // witch, broom
 ```
 
 To clearly understand the change, let's trace the search step by step.
@@ -175,11 +175,11 @@ With regexps, there's often more than one way to do the same thing.
 In our case we can find quoted strings without lazy mode using the regexp `pattern:"[^"]+"`:
 
 ```js run
-let reg = /"[^"]+"/g;
+let regexp = /"[^"]+"/g;
 
 let str = 'a "witch" and her "broom" is one';
 
-alert( str.match(reg) ); // witch, broom
+alert( str.match(regexp) ); // witch, broom
 ```
 
 The regexp `pattern:"[^"]+"` gives correct results, because it looks for a quote `pattern:'"'` followed by one or more non-quotes `pattern:[^"]`, and then the closing quote.
@@ -201,20 +201,20 @@ The first idea might be: `pattern:/<a href=".*" class="doc">/g`.
 Let's check it:
 ```js run
 let str = '...<a href="link" class="doc">...';
-let reg = /<a href=".*" class="doc">/g;
+let regexp = /<a href=".*" class="doc">/g;
 
 // Works!
-alert( str.match(reg) ); // <a href="link" class="doc">
+alert( str.match(regexp) ); // <a href="link" class="doc">
 ```
 
 It worked. But let's see what happens if there are many links in the text?
 
 ```js run
 let str = '...<a href="link1" class="doc">... <a href="link2" class="doc">...';
-let reg = /<a href=".*" class="doc">/g;
+let regexp = /<a href=".*" class="doc">/g;
 
 // Whoops! Two links in one match!
-alert( str.match(reg) ); // <a href="link1" class="doc">... <a href="link2" class="doc">
+alert( str.match(regexp) ); // <a href="link1" class="doc">... <a href="link2" class="doc">
 ```
 
 Now the result is wrong for the same reason as our "witches" example. The quantifier `pattern:.*` took too many characters.
@@ -230,10 +230,10 @@ Let's modify the pattern by making the quantifier `pattern:.*?` lazy:
 
 ```js run
 let str = '...<a href="link1" class="doc">... <a href="link2" class="doc">...';
-let reg = /<a href=".*?" class="doc">/g;
+let regexp = /<a href=".*?" class="doc">/g;
 
 // Works!
-alert( str.match(reg) ); // <a href="link1" class="doc">, <a href="link2" class="doc">
+alert( str.match(regexp) ); // <a href="link1" class="doc">, <a href="link2" class="doc">
 ```
 
 Now it seems to work, there are two matches:
@@ -247,10 +247,10 @@ Now it seems to work, there are two matches:
 
 ```js run
 let str = '...<a href="link1" class="wrong">... <p style="" class="doc">...';
-let reg = /<a href=".*?" class="doc">/g;
+let regexp = /<a href=".*?" class="doc">/g;
 
 // Wrong match!
-alert( str.match(reg) ); // <a href="link1" class="wrong">... <p style="" class="doc">
+alert( str.match(regexp) ); // <a href="link1" class="wrong">... <p style="" class="doc">
 ```
 
 Now it fails. The match includes not just a link, but also a lot of text after it, including `<p...>`.
@@ -281,11 +281,11 @@ A working example:
 ```js run
 let str1 = '...<a href="link1" class="wrong">... <p style="" class="doc">...';
 let str2 = '...<a href="link1" class="doc">... <a href="link2" class="doc">...';
-let reg = /<a href="[^"]*" class="doc">/g;
+let regexp = /<a href="[^"]*" class="doc">/g;
 
 // Works!
-alert( str1.match(reg) ); // null, no matches, that's correct
-alert( str2.match(reg) ); // <a href="link1" class="doc">, <a href="link2" class="doc">
+alert( str1.match(regexp) ); // null, no matches, that's correct
+alert( str2.match(regexp) ); // <a href="link1" class="doc">, <a href="link2" class="doc">
 ```
 
 ## Summary
diff --git a/9-regular-expressions/11-regexp-groups/01-test-mac/solution.md b/9-regular-expressions/11-regexp-groups/01-test-mac/solution.md
index c16f0565..26f7888f 100644
--- a/9-regular-expressions/11-regexp-groups/01-test-mac/solution.md
+++ b/9-regular-expressions/11-regexp-groups/01-test-mac/solution.md
@@ -9,13 +9,13 @@ Now let's show that the match should capture all the text: start at the beginnin
 Finally:
 
 ```js run
-let reg = /^[0-9a-fA-F]{2}(:[0-9a-fA-F]{2}){5}$/i;
+let regexp = /^[0-9a-fA-F]{2}(:[0-9a-fA-F]{2}){5}$/i;
 
-alert( reg.test('01:32:54:67:89:AB') ); // true
+alert( regexp.test('01:32:54:67:89:AB') ); // true
 
-alert( reg.test('0132546789AB') ); // false (no colons)
+alert( regexp.test('0132546789AB') ); // false (no colons)
 
-alert( reg.test('01:32:54:67:89') ); // false (5 numbers, need 6)
+alert( regexp.test('01:32:54:67:89') ); // false (5 numbers, need 6)
 
-alert( reg.test('01:32:54:67:89:ZZ') ) // false (ZZ in the end)
+alert( regexp.test('01:32:54:67:89:ZZ') ) // false (ZZ in the end)
 ```
diff --git a/9-regular-expressions/11-regexp-groups/01-test-mac/task.md b/9-regular-expressions/11-regexp-groups/01-test-mac/task.md
index e7265598..029a4803 100644
--- a/9-regular-expressions/11-regexp-groups/01-test-mac/task.md
+++ b/9-regular-expressions/11-regexp-groups/01-test-mac/task.md
@@ -8,13 +8,13 @@ Write a regexp that checks whether a string is MAC-address.
 
 Usage:
 ```js
-let reg = /your regexp/;
+let regexp = /your regexp/;
 
-alert( reg.test('01:32:54:67:89:AB') ); // true
+alert( regexp.test('01:32:54:67:89:AB') ); // true
 
-alert( reg.test('0132546789AB') ); // false (no colons)
+alert( regexp.test('0132546789AB') ); // false (no colons)
 
-alert( reg.test('01:32:54:67:89') ); // false (5 numbers, must be 6)
+alert( regexp.test('01:32:54:67:89') ); // false (5 numbers, must be 6)
 
-alert( reg.test('01:32:54:67:89:ZZ') ) // false (ZZ ad the end)
+alert( regexp.test('01:32:54:67:89:ZZ') ) // false (ZZ ad the end)
 ```
diff --git a/9-regular-expressions/11-regexp-groups/02-find-webcolor-3-or-6/solution.md b/9-regular-expressions/11-regexp-groups/02-find-webcolor-3-or-6/solution.md
index e173aba6..0806dc4f 100644
--- a/9-regular-expressions/11-regexp-groups/02-find-webcolor-3-or-6/solution.md
+++ b/9-regular-expressions/11-regexp-groups/02-find-webcolor-3-or-6/solution.md
@@ -9,19 +9,19 @@ Here the pattern `pattern:[a-f0-9]{3}` is enclosed in parentheses to apply the q
 In action:
 
 ```js run
-let reg = /#([a-f0-9]{3}){1,2}/gi;
+let regexp = /#([a-f0-9]{3}){1,2}/gi;
 
 let str = "color: #3f3; background-color: #AA00ef; and: #abcd";
 
-alert( str.match(reg) ); // #3f3 #AA00ef #abc
+alert( str.match(regexp) ); // #3f3 #AA00ef #abc
 ```
 
 There's a minor problem here: the pattern found `match:#abc` in `subject:#abcd`. To prevent that we can add `pattern:\b` to the end:
 
 ```js run
-let reg = /#([a-f0-9]{3}){1,2}\b/gi;
+let regexp = /#([a-f0-9]{3}){1,2}\b/gi;
 
 let str = "color: #3f3; background-color: #AA00ef; and: #abcd";
 
-alert( str.match(reg) ); // #3f3 #AA00ef
+alert( str.match(regexp) ); // #3f3 #AA00ef
 ```
diff --git a/9-regular-expressions/11-regexp-groups/02-find-webcolor-3-or-6/task.md b/9-regular-expressions/11-regexp-groups/02-find-webcolor-3-or-6/task.md
index d87914e9..09108484 100644
--- a/9-regular-expressions/11-regexp-groups/02-find-webcolor-3-or-6/task.md
+++ b/9-regular-expressions/11-regexp-groups/02-find-webcolor-3-or-6/task.md
@@ -4,11 +4,11 @@ Write a RegExp that matches colors in the format `#abc` or `#abcdef`. That is: `
 
 Usage example:
 ```js
-let reg = /your regexp/g;
+let regexp = /your regexp/g;
 
 let str = "color: #3f3; background-color: #AA00ef; and: #abcd";
 
-alert( str.match(reg) ); // #3f3 #AA00ef
+alert( str.match(regexp) ); // #3f3 #AA00ef
 ```
 
 P.S. This should be exactly 3 or 6 hex digits. Values with 4 digits, such as `#abcd`, should not match.
diff --git a/9-regular-expressions/11-regexp-groups/03-find-decimal-numbers/solution.md b/9-regular-expressions/11-regexp-groups/03-find-decimal-numbers/solution.md
index 3155f13c..c4349f9a 100644
--- a/9-regular-expressions/11-regexp-groups/03-find-decimal-numbers/solution.md
+++ b/9-regular-expressions/11-regexp-groups/03-find-decimal-numbers/solution.md
@@ -3,9 +3,9 @@ A positive number with an optional decimal part is (per previous task): `pattern
 Let's add the optional `pattern:-` in the beginning:
 
 ```js run
-let reg = /-?\d+(\.\d+)?/g;
+let regexp = /-?\d+(\.\d+)?/g;
 
 let str = "-1.5 0 2 -123.4.";
 
-alert( str.match(reg) );   // -1.5, 0, 2, -123.4
+alert( str.match(regexp) );   // -1.5, 0, 2, -123.4
 ```
diff --git a/9-regular-expressions/11-regexp-groups/03-find-decimal-numbers/task.md b/9-regular-expressions/11-regexp-groups/03-find-decimal-numbers/task.md
index 45935068..4f5a73ff 100644
--- a/9-regular-expressions/11-regexp-groups/03-find-decimal-numbers/task.md
+++ b/9-regular-expressions/11-regexp-groups/03-find-decimal-numbers/task.md
@@ -5,9 +5,9 @@ Write a regexp that looks for all decimal numbers including integer ones, with t
 An example of use:
 
 ```js
-let reg = /your regexp/g;
+let regexp = /your regexp/g;
 
 let str = "-1.5 0 2 -123.4.";
 
-alert( str.match(reg) ); // -1.5, 0, 2, -123.4
+alert( str.match(regexp) ); // -1.5, 0, 2, -123.4
 ```
diff --git a/9-regular-expressions/11-regexp-groups/04-parse-expression/solution.md b/9-regular-expressions/11-regexp-groups/04-parse-expression/solution.md
index decb074d..130c57be 100644
--- a/9-regular-expressions/11-regexp-groups/04-parse-expression/solution.md
+++ b/9-regular-expressions/11-regexp-groups/04-parse-expression/solution.md
@@ -18,9 +18,9 @@ To make each of these parts a separate element of the result array, let's enclos
 In action:
 
 ```js run
-let reg = /(-?\d+(\.\d+)?)\s*([-+*\/])\s*(-?\d+(\.\d+)?)/;
+let regexp = /(-?\d+(\.\d+)?)\s*([-+*\/])\s*(-?\d+(\.\d+)?)/;
 
-alert( "1.2 + 12".match(reg) );
+alert( "1.2 + 12".match(regexp) );
 ```
 
 The result includes:
@@ -42,9 +42,9 @@ The final solution:
 
 ```js run
 function parse(expr) {
-  let reg = /(-?\d+(?:\.\d+)?)\s*([-+*\/])\s*(-?\d+(?:\.\d+)?)/;
+  let regexp = /(-?\d+(?:\.\d+)?)\s*([-+*\/])\s*(-?\d+(?:\.\d+)?)/;
 
-  let result = expr.match(reg);
+  let result = expr.match(regexp);
 
   if (!result) return [];
   result.shift();
diff --git a/9-regular-expressions/11-regexp-groups/article.md b/9-regular-expressions/11-regexp-groups/article.md
index 8a4fdd71..acc59b7c 100644
--- a/9-regular-expressions/11-regexp-groups/article.md
+++ b/9-regular-expressions/11-regexp-groups/article.md
@@ -56,9 +56,9 @@ The email format is: `name@domain`. Any word can be the name, hyphens and dots a
 The pattern:
 
 ```js run
-let reg = /[-.\w]+@([\w-]+\.)+[\w-]+/g;
+let regexp = /[-.\w]+@([\w-]+\.)+[\w-]+/g;
 
-alert("my@mail.com @ his@site.com.uk".match(reg)); // my@mail.com, his@site.com.uk
+alert("my@mail.com @ his@site.com.uk".match(regexp)); // my@mail.com, his@site.com.uk
 ```
 
 That regexp is not perfect, but mostly works and helps to fix accidental mistypes. The only truly reliable check for an email can only be done by sending a letter.
@@ -110,9 +110,9 @@ In action:
 ```js run
 let str = '<span class="my">';
 
-let reg = /<(([a-z]+)\s*([^>]*))>/;
+let regexp = /<(([a-z]+)\s*([^>]*))>/;
 
-let result = str.match(reg);
+let result = str.match(regexp);
 alert(result[0]); // <span class="my">
 alert(result[1]); // span class="my"
 alert(result[2]); // span
@@ -336,10 +336,10 @@ let str = "Gogogo John!";
 
 *!*
 // ?: exludes 'go' from capturing
-let reg = /(?:go)+ (\w+)/i;
+let regexp = /(?:go)+ (\w+)/i;
 */!*
 
-let result = str.match(reg);
+let result = str.match(regexp);
 
 alert( result[0] ); // Gogogo John (full match)
 alert( result[1] ); // John
diff --git a/9-regular-expressions/12-regexp-backreferences/article.md b/9-regular-expressions/12-regexp-backreferences/article.md
index 07d2ca07..83beb803 100644
--- a/9-regular-expressions/12-regexp-backreferences/article.md
+++ b/9-regular-expressions/12-regexp-backreferences/article.md
@@ -17,10 +17,10 @@ We can put both kinds of quotes in the square brackets: `pattern:['"](.*?)['"]`,
 ```js run
 let str = `He said: "She's the one!".`;
 
-let reg = /['"](.*?)['"]/g;
+let regexp = /['"](.*?)['"]/g;
 
 // The result is not what we'd like to have
-alert( str.match(reg) ); // "She'
+alert( str.match(regexp) ); // "She'
 ```
 
 As we can see, the pattern found an opening quote `match:"`, then the text is consumed till the other quote `match:'`, that closes the match.
@@ -33,10 +33,10 @@ Here's the correct code:
 let str = `He said: "She's the one!".`;
 
 *!*
-let reg = /(['"])(.*?)\1/g;
+let regexp = /(['"])(.*?)\1/g;
 */!*
 
-alert( str.match(reg) ); // "She's the one!"
+alert( str.match(regexp) ); // "She's the one!"
 ```
 
 Now it works! The regular expression engine finds the first quote `pattern:(['"])` and memorizes its content. That's the first capturing group.
@@ -65,8 +65,8 @@ In the example below the group with quotes is named `pattern:?<quote>`, so the b
 let str = `He said: "She's the one!".`;
 
 *!*
-let reg = /(?<quote>['"])(.*?)\k<quote>/g;
+let regexp = /(?<quote>['"])(.*?)\k<quote>/g;
 */!*
 
-alert( str.match(reg) ); // "She's the one!"
+alert( str.match(regexp) ); // "She's the one!"
 ```
diff --git a/9-regular-expressions/13-regexp-alternation/01-find-programming-language/solution.md b/9-regular-expressions/13-regexp-alternation/01-find-programming-language/solution.md
index 3419aa49..e33f9cf2 100644
--- a/9-regular-expressions/13-regexp-alternation/01-find-programming-language/solution.md
+++ b/9-regular-expressions/13-regexp-alternation/01-find-programming-language/solution.md
@@ -4,11 +4,11 @@ The first idea can be to list the languages with `|` in-between.
 But that doesn't work right:
 
 ```js run
-let reg = /Java|JavaScript|PHP|C|C\+\+/g;
+let regexp = /Java|JavaScript|PHP|C|C\+\+/g;
 
 let str = "Java, JavaScript, PHP, C, C++";
 
-alert( str.match(reg) ); // Java,Java,PHP,C,C
+alert( str.match(regexp) ); // Java,Java,PHP,C,C
 ```
 
 The regular expression engine looks for alternations one-by-one. That is: first it checks if we have  `match:Java`, otherwise -- looks for `match:JavaScript` and so on.
@@ -25,9 +25,9 @@ There are two solutions for that problem:
 In action:
 
 ```js run
-let reg = /Java(Script)?|C(\+\+)?|PHP/g;
+let regexp = /Java(Script)?|C(\+\+)?|PHP/g;
 
 let str = "Java, JavaScript, PHP, C, C++";
 
-alert( str.match(reg) ); // Java,JavaScript,PHP,C,C++
+alert( str.match(regexp) ); // Java,JavaScript,PHP,C,C++
 ```
diff --git a/9-regular-expressions/13-regexp-alternation/01-find-programming-language/task.md b/9-regular-expressions/13-regexp-alternation/01-find-programming-language/task.md
index 61b9526f..e0f7af95 100644
--- a/9-regular-expressions/13-regexp-alternation/01-find-programming-language/task.md
+++ b/9-regular-expressions/13-regexp-alternation/01-find-programming-language/task.md
@@ -5,7 +5,7 @@ There are many programming languages, for instance Java, JavaScript, PHP, C, C++
 Create a regexp that finds them in the string `subject:Java JavaScript PHP C++ C`:
 
 ```js
-let reg = /your regexp/g;
+let regexp = /your regexp/g;
 
-alert("Java JavaScript PHP C++ C".match(reg)); // Java JavaScript PHP C++ C
+alert("Java JavaScript PHP C++ C".match(regexp)); // Java JavaScript PHP C++ C
 ```
diff --git a/9-regular-expressions/13-regexp-alternation/02-find-matching-bbtags/solution.md b/9-regular-expressions/13-regexp-alternation/02-find-matching-bbtags/solution.md
index dddaf962..971e2e62 100644
--- a/9-regular-expressions/13-regexp-alternation/02-find-matching-bbtags/solution.md
+++ b/9-regular-expressions/13-regexp-alternation/02-find-matching-bbtags/solution.md
@@ -8,7 +8,7 @@ The full pattern: `pattern:\[(b|url|quote)\].*?\[/\1\]`.
 In action:
 
 ```js run
-let reg = /\[(b|url|quote)\].*?\[\/\1\]/gs;
+let regexp = /\[(b|url|quote)\].*?\[\/\1\]/gs;
 
 let str = `
   [b]hello![/b]
@@ -17,7 +17,7 @@ let str = `
   [/quote]
 `;
 
-alert( str.match(reg) ); // [b]hello![/b],[quote][url]http://google.com[/url][/quote]
+alert( str.match(regexp) ); // [b]hello![/b],[quote][url]http://google.com[/url][/quote]
 ```
 
 Please note that we had to escape a slash for the closing tag `pattern:[/\1]`, because normally the slash closes the pattern.
diff --git a/9-regular-expressions/13-regexp-alternation/02-find-matching-bbtags/task.md b/9-regular-expressions/13-regexp-alternation/02-find-matching-bbtags/task.md
index 8cc59deb..2893a450 100644
--- a/9-regular-expressions/13-regexp-alternation/02-find-matching-bbtags/task.md
+++ b/9-regular-expressions/13-regexp-alternation/02-find-matching-bbtags/task.md
@@ -32,17 +32,17 @@ Create a regexp to find all BB-tags with their contents.
 For instance:
 
 ```js
-let reg = /your regexp/flags;
+let regexp = /your regexp/flags;
 
 let str = "..[url]http://google.com[/url]..";
-alert( str.match(reg) ); // [url]http://google.com[/url]
+alert( str.match(regexp) ); // [url]http://google.com[/url]
 ```
 
 If tags are nested, then we need the outer tag (if we want we can continue the search in its content):
 
 ```js
-let reg = /your regexp/flags;
+let regexp = /your regexp/flags;
 
 let str = "..[url][b]http://google.com[/b][/url]..";
-alert( str.match(reg) ); // [url][b]http://google.com[/b][/url]
+alert( str.match(regexp) ); // [url][b]http://google.com[/b][/url]
 ```
diff --git a/9-regular-expressions/13-regexp-alternation/03-match-quoted-string/solution.md b/9-regular-expressions/13-regexp-alternation/03-match-quoted-string/solution.md
index 143be870..5a007aee 100644
--- a/9-regular-expressions/13-regexp-alternation/03-match-quoted-string/solution.md
+++ b/9-regular-expressions/13-regexp-alternation/03-match-quoted-string/solution.md
@@ -10,8 +10,8 @@ Step by step:
 In action:
 
 ```js run
-let reg = /"(\\.|[^"\\])*"/g;
+let regexp = /"(\\.|[^"\\])*"/g;
 let str = ' .. "test me" .. "Say \\"Hello\\"!" .. "\\\\ \\"" .. ';
 
-alert( str.match(reg) ); // "test me","Say \"Hello\"!","\\ \""
+alert( str.match(regexp) ); // "test me","Say \"Hello\"!","\\ \""
 ```
diff --git a/9-regular-expressions/13-regexp-alternation/04-match-exact-tag/solution.md b/9-regular-expressions/13-regexp-alternation/04-match-exact-tag/solution.md
index 70c4de91..5d4ba8d9 100644
--- a/9-regular-expressions/13-regexp-alternation/04-match-exact-tag/solution.md
+++ b/9-regular-expressions/13-regexp-alternation/04-match-exact-tag/solution.md
@@ -10,7 +10,7 @@ In the regexp language: `pattern:<style(>|\s.*?>)`.
 In action:
 
 ```js run
-let reg = /<style(>|\s.*?>)/g;
+let regexp = /<style(>|\s.*?>)/g;
 
-alert( '<style> <styler> <style test="...">'.match(reg) ); // <style>, <style test="...">
+alert( '<style> <styler> <style test="...">'.match(regexp) ); // <style>, <style test="...">
 ```
diff --git a/9-regular-expressions/13-regexp-alternation/04-match-exact-tag/task.md b/9-regular-expressions/13-regexp-alternation/04-match-exact-tag/task.md
index 85976a9e..e8a9e31b 100644
--- a/9-regular-expressions/13-regexp-alternation/04-match-exact-tag/task.md
+++ b/9-regular-expressions/13-regexp-alternation/04-match-exact-tag/task.md
@@ -7,7 +7,7 @@ Write a regexp to find the tag `<style...>`. It should match the full tag: it ma
 For instance:
 
 ```js
-let reg = /your regexp/g;
+let regexp = /your regexp/g;
 
-alert( '<style> <styler> <style test="...">'.match(reg) ); // <style>, <style test="...">
+alert( '<style> <styler> <style test="...">'.match(regexp) ); // <style>, <style test="...">
 ```
diff --git a/9-regular-expressions/13-regexp-alternation/article.md b/9-regular-expressions/13-regexp-alternation/article.md
index 5dcb9e86..007d8f6a 100644
--- a/9-regular-expressions/13-regexp-alternation/article.md
+++ b/9-regular-expressions/13-regexp-alternation/article.md
@@ -11,11 +11,11 @@ The corresponding regexp: `pattern:html|php|java(script)?`.
 A usage example:
 
 ```js run
-let reg = /html|php|css|java(script)?/gi;
+let regexp = /html|php|css|java(script)?/gi;
 
 let str = "First HTML appeared, then CSS, then JavaScript";
 
-alert( str.match(reg) ); // 'HTML', 'CSS', 'JavaScript'
+alert( str.match(regexp) ); // 'HTML', 'CSS', 'JavaScript'
 ```
 
 We already saw a similar thing -- square brackets. They allow to choose between multiple characters, for instance `pattern:gr[ae]y` matches `match:gray` or `match:grey`.
@@ -64,7 +64,7 @@ But that's wrong, the alternation should only be used in the "hours" part of the
 The final solution:
 
 ```js run
-let reg = /([01]\d|2[0-3]):[0-5]\d/g;
+let regexp = /([01]\d|2[0-3]):[0-5]\d/g;
 
-alert("00:00 10:10 23:59 25:99 1:2".match(reg)); // 00:00,10:10,23:59
+alert("00:00 10:10 23:59 25:99 1:2".match(regexp)); // 00:00,10:10,23:59
 ```
diff --git a/9-regular-expressions/14-regexp-lookahead-lookbehind/1-find-non-negative-integers/solution.md b/9-regular-expressions/14-regexp-lookahead-lookbehind/1-find-non-negative-integers/solution.md
index aa62aca1..a824409f 100644
--- a/9-regular-expressions/14-regexp-lookahead-lookbehind/1-find-non-negative-integers/solution.md
+++ b/9-regular-expressions/14-regexp-lookahead-lookbehind/1-find-non-negative-integers/solution.md
@@ -6,11 +6,11 @@ We can exclude negatives by prepending it with the negative lookahead: `pattern:
 Although, if we try it now, we may notice one more "extra" result:
 
 ```js run
-let reg = /(?<!-)\d+/g;
+let regexp = /(?<!-)\d+/g;
 
 let str = "0 12 -5 123 -18";
 
-console.log( str.match(reg) ); // 0, 12, 123, *!*8*/!*
+console.log( str.match(regexp) ); // 0, 12, 123, *!*8*/!*
 ```
 
 As you can see, it matches `match:8`, from `subject:-18`. To exclude it, we need to ensure that the regexp starts matching a number not from the middle of another (non-matching) number.
@@ -20,9 +20,9 @@ We can do it by specifying another negative lookbehind: `pattern:(?<!-)(?<!\d)\d
 We can also join them into a single lookbehind here:
 
 ```js run
-let reg = /(?<![-\d])\d+/g;
+let regexp = /(?<![-\d])\d+/g;
 
 let str = "0 12 -5 123 -18";
 
-alert( str.match(reg) ); // 0, 12, 123
+alert( str.match(regexp) ); // 0, 12, 123
 ```
diff --git a/9-regular-expressions/14-regexp-lookahead-lookbehind/1-find-non-negative-integers/task.md b/9-regular-expressions/14-regexp-lookahead-lookbehind/1-find-non-negative-integers/task.md
index 1508d6d5..cd58f992 100644
--- a/9-regular-expressions/14-regexp-lookahead-lookbehind/1-find-non-negative-integers/task.md
+++ b/9-regular-expressions/14-regexp-lookahead-lookbehind/1-find-non-negative-integers/task.md
@@ -6,9 +6,9 @@ Create a regexp that looks for only non-negative ones (zero is allowed).
 
 An example of use:
 ```js
-let reg = /your regexp/g;
+let regexp = /your regexp/g;
 
 let str = "0 12 -5 123 -18";
 
-alert( str.match(reg) ); // 0, 12, 123
+alert( str.match(regexp) ); // 0, 12, 123
 ```
diff --git a/9-regular-expressions/14-regexp-lookahead-lookbehind/2-insert-after-head/task.md b/9-regular-expressions/14-regexp-lookahead-lookbehind/2-insert-after-head/task.md
index 7bdfcd67..ac9e5e4c 100644
--- a/9-regular-expressions/14-regexp-lookahead-lookbehind/2-insert-after-head/task.md
+++ b/9-regular-expressions/14-regexp-lookahead-lookbehind/2-insert-after-head/task.md
@@ -7,7 +7,7 @@
 Например:
 
 ```js
-let reg = /ваше регулярное выражение/;
+let regexp = /ваше регулярное выражение/;
 
 let str = `
 <html>
@@ -17,7 +17,7 @@ let str = `
 </html>
 `;
 
-str = str.replace(reg, `<h1>Hello</h1>`);
+str = str.replace(regexp, `<h1>Hello</h1>`);
 ```
 
 После этого значение `str`:
diff --git a/9-regular-expressions/14-regexp-lookahead-lookbehind/article.md b/9-regular-expressions/14-regexp-lookahead-lookbehind/article.md
index 1115c502..31393cd0 100644
--- a/9-regular-expressions/14-regexp-lookahead-lookbehind/article.md
+++ b/9-regular-expressions/14-regexp-lookahead-lookbehind/article.md
@@ -96,18 +96,18 @@ In the example below the currency sign `pattern:(€|kr)` is captured, along wit
 
 ```js run
 let str = "1 turkey costs 30€";
-let reg = /\d+(?=(€|kr))/; // extra parentheses around €|kr
+let regexp = /\d+(?=(€|kr))/; // extra parentheses around €|kr
 
-alert( str.match(reg) ); // 30, €
+alert( str.match(regexp) ); // 30, €
 ```
 
 And here's the same for lookbehind:
 
 ```js run
 let str = "1 turkey costs $30";
-let reg = /(?<=(\$|£))\d+/;
+let regexp = /(?<=(\$|£))\d+/;
 
-alert( str.match(reg) ); // 30, $
+alert( str.match(regexp) ); // 30, $
 ```
 
 ## Summary
diff --git a/9-regular-expressions/15-regexp-catastrophic-backtracking/article.md b/9-regular-expressions/15-regexp-catastrophic-backtracking/article.md
index 57c60ff3..59467f93 100644
--- a/9-regular-expressions/15-regexp-catastrophic-backtracking/article.md
+++ b/9-regular-expressions/15-regexp-catastrophic-backtracking/article.md
@@ -19,10 +19,10 @@ We'll use a regexp `pattern:^(\w+\s?)*$`, it specifies 0 or more such words.
 In action:
 
 ```js run
-let reg = /^(\w+\s?)*$/;
+let regexp = /^(\w+\s?)*$/;
 
-alert( reg.test("A good string") ); // true
-alert( reg.test("Bad characters: $@#") ); // false
+alert( regexp.test("A good string") ); // true
+alert( regexp.test("Bad characters: $@#") ); // false
 ```
 
 It seems to work. The result is correct. Although, on certain strings it takes a lot of time. So long that JavaScript engine "hangs" with 100% CPU consumption.
@@ -30,11 +30,11 @@ It seems to work. The result is correct. Although, on certain strings it takes a
 If you run the example below, you probably won't see anything, as JavaScript will just "hang". A web-browser will stop reacting on events, the UI will stop working. After some time it will suggest to reloaad the page. So be careful with this:
 
 ```js run
-let reg = /^(\w+\s?)*$/;
+let regexp = /^(\w+\s?)*$/;
 let str = "An input string that takes a long time or even makes this regexp to hang!";
 
 // will take a very long time
-alert( reg.test(str) );
+alert( regexp.test(str) );
 ```
 
 Some regular expression engines can handle such search, but most of them can't.
@@ -50,12 +50,12 @@ And, to make things more obvious, let's replace `pattern:\w` with `pattern:\d`.
 <!-- let str = `AnInputStringThatMakesItHang!`; -->
 
 ```js run
-let reg = /^(\d+)*$/;
+let regexp = /^(\d+)*$/;
 
 let str = "012345678901234567890123456789!";
 
 // will take a very long time
-alert( reg.test(str) );
+alert( regexp.test(str) );
 ```
 
 So what's wrong with the regexp?
@@ -189,10 +189,10 @@ Let's rewrite the regular expression as `pattern:^(\w+\s)*\w*` - we'll look for
 This regexp is equivalent to the previous one (matches the same) and works well:
 
 ```js run
-let reg = /^(\w+\s)*\w*$/;
+let regexp = /^(\w+\s)*\w*$/;
 let str = "An input string that takes a long time or even makes this regex to hang!";
 
-alert( reg.test(str) ); // false
+alert( regexp.test(str) ); // false
 ```
 
 Why did the problem disappear?
@@ -272,26 +272,26 @@ There's more about the relation between possessive quantifiers and lookahead in
 Let's rewrite the first example using lookahead to prevent backtracking:
 
 ```js run
-let reg = /^((?=(\w+))\2\s?)*$/;
+let regexp = /^((?=(\w+))\2\s?)*$/;
 
-alert( reg.test("A good string") ); // true
+alert( regexp.test("A good string") ); // true
 
 let str = "An input string that takes a long time or even makes this regex to hang!";
 
-alert( reg.test(str) ); // false, works and fast!
+alert( regexp.test(str) ); // false, works and fast!
 ```
 
 Here `pattern:\2` is used instead of `pattern:\1`, because there are additional outer parentheses. To avoid messing up with the numbers, we can give the parentheses a name, e.g. `pattern:(?<word>\w+)`.
 
 ```js run
 // parentheses are named ?<word>, referenced as \k<word>
-let reg = /^((?=(?<word>\w+))\k<word>\s?)*$/;
+let regexp = /^((?=(?<word>\w+))\k<word>\s?)*$/;
 
 let str = "An input string that takes a long time or even makes this regex to hang!";
 
-alert( reg.test(str) ); // false
+alert( regexp.test(str) ); // false
 
-alert( reg.test("A correct string") ); // true
+alert( regexp.test("A correct string") ); // true
 ```
 
 The problem described in this article is called "catastrophic backtracking".
diff --git a/9-regular-expressions/17-regexp-methods/article.md b/9-regular-expressions/17-regexp-methods/article.md
index 1017eb06..00bc7f2f 100644
--- a/9-regular-expressions/17-regexp-methods/article.md
+++ b/9-regular-expressions/17-regexp-methods/article.md
@@ -71,9 +71,9 @@ Usage example:
 
 ```js run
 let str = '<h1>Hello, world!</h1>';
-let reg = /<(.*?)>/g;
+let regexp = /<(.*?)>/g;
 
-let matchAll = str.matchAll(reg);
+let matchAll = str.matchAll(regexp);
 
 alert(matchAll); // [object RegExp String Iterator], not array, but an iterable
 
@@ -118,7 +118,7 @@ alert( str.search( /ink/i ) ); // 10 (first match position)
 
 If we need positions of further matches, we should use other means, such as finding them all with `str.matchAll(regexp)`.
 
-## str.replace(str|reg, str|func)
+## str.replace(str|regexp, str|func)
 
 This is a generic method for searching and replacing, one of most useful ones. The swiss army knife for searching and replacing.  
 
@@ -238,7 +238,7 @@ The method `regexp.exec(str)` method returns a match for `regexp` in the string
 
 It behaves differently depending on whether the regexp has flag `pattern:g`.
 
-If there's no `pattern:g`, then `regexp.exec(str)` returns the first match exactly as  `str.match(reg)`. This behavior doesn't bring anything new.
+If there's no `pattern:g`, then `regexp.exec(str)` returns the first match exactly as  `str.match(regexp)`. This behavior doesn't bring anything new.
 
 But if there's flag `pattern:g`, then:
 - A call to `regexp.exec(str)` returns the first match and saves the position immediately after it in the property `regexp.lastIndex`.
@@ -272,7 +272,7 @@ For instance:
 ```js run
 let str = 'Hello, world!';
 
-let reg = /\w+/g; // without flag "g", lastIndex property is ignored
+let regexp = /\w+/g; // without flag "g", lastIndex property is ignored
 regexp.lastIndex = 5; // search from 5th position (from the comma)
 
 alert( regexp.exec(str) ); // world
@@ -285,7 +285,7 @@ Let's replace flag `pattern:g` with `pattern:y` in the example above. There will
 ```js run
 let str = 'Hello, world!';
 
-let reg = /\w+/y;
+let regexp = /\w+/y;
 regexp.lastIndex = 5; // search exactly at position 5
 
 alert( regexp.exec(str) ); // null