Fix Grammer

1-js/06-advanced-functions/08-settimeout-setinterval/article.md

@@ -75,7 +75,7 @@ Novice developers sometimes make a mistake by adding brackets `()` after the fun
 // wrong!
 setTimeout(sayHi(), 1000);
 ```
-That doesn't work, because `setTimeout` expects a reference to function. And here `sayHi()` runs the function, and the *result of its execution* is passed to `setTimeout`. In our case the result of `sayHi()` is `undefined` (the function returns nothing), so nothing is scheduled.
+That doesn't work, because `setTimeout` expects a reference to a function. And here `sayHi()` runs the function, and the *result of its execution* is passed to `setTimeout`. In our case the result of `sayHi()` is `undefined` (the function returns nothing), so nothing is scheduled.
 ````
 
 ### Canceling with clearTimeout