Conventions of Composition Rule 150

Rules: Adverbs modify verbs, adjectives and other adverbs. Adjectives modify nouns and pronouns. An adjective must not be used adverbially (as a modifier of a verb, adjective, infinitive, or participle).

Examples:

Correct: He ran easily, well, ill, badly, hard, fast, etc.

Correct [comparative and superlative forms]: He jogged more easily, most easily, harder, fastest, etc.

Practice deciding whether to use an adjective or an adverb:

1. Their quickly swimming made them the better water polo team.
2. Frankie reads so easy and fluent that nobody can believe he's only four.
3. If the child behaves good, he can often earn more privileges.
4. Ever since recovering from her horrible head cold, Harley smells good again.

Resources for further explanation of the differences between adjectives and adverbs:

Purdue OWL's The Difference between Adjectives and Adverbs

Grammar Book's Adjectives and Adverbs