One of the most common errors in spoken English, made even by educated people, is the misuse of adjectives in the place of adverbs:
“They need to push forward much quicker.”
I’ll give you a moment to try to figure out the grammar issue, and then I’ll reveal it in the next paragraph…
The problem here is that the word being modified by “quicker” is “push,” which is a verb. “Quicker” is an adjective (a comparative), and adjectives cannot modify verbs. People will certainly know what you’re trying to say, but it does not sound quite kosher, and lacks the elegance of a grammatically correct sentence.
Here is the correct fix:
“They need to push forward much more quickly.”
Doesn’t that sound much better?
If you have trouble remembering what an adverb is, keep in mind that they often have the suffix “ly” (but not always, in which case it’s known as a “flat adverb,” like “fast”).
Here’s another one:
We need to clear the hallways faster.
And the fix:
We need to clear the hallways more quickly.
Once again, as an adjective, faster cannot modify “clear”; whereas “more quickly” gets the job done!
This concept is a good illustration of why a basic understanding of grammar is necessary in order to speak properly. Without knowing the parts of speech, it would be impossible to describe and to understand why only adverbs can modify verbs.