Conventions of Composition Rule 151

Rules: An adverb must not be used as a predicate adjective (to describe, after the verb, the quality or condition of the subject).

Examples:

Correct: The flowers smell sweet [not sweetly].

Correct: I feel well [well is an adjective in the sense of in good health].

Wrong: I feel badly today, so I will try to get some rest.

Correct: I fell ill [ill is an adjective in the sense of in bad health].

Practice fixing predicate adjective errors:

1. While last week I felt pretty sickly, today, I am good.
2. Reese looks prettily in that dress.
3. Do you think the soup tastes superbly today?
4. The team's cheer sounds loudly in this echoey room.

Resources for further explanation of why adverbs can't be used as predicate adjectives:

Soft Schools' Predicate Adjectives

UCL's Adjectives and Predicate Adjectives