Adjectives describe nouns; adverbs describe verbs, adjectives, and other adverbs. “A quick runner” (adjective describing the noun runner) vs “she runs quickly” (adverb describing the verb runs). Mixing them up is one of the most common grammar slips — here’s how to keep them straight.
The core difference
- Adjective → noun. It tells you which, what kind, or how many: a red car, a careful writer, three options.
- Adverb → verb / adjective / adverb. It tells you how, when, where, or to what extent: she wrote carefully, very clear, runs fast.
Quick test: if the word is describing a thing, it’s an adjective; if it’s describing an action (or a quality/another adverb), it’s an adverb.
The -ly trap
Many adverbs end in -ly (quick → quickly), but not all:
- Some adverbs don’t end in -ly: fast, hard, well, late. “Drive fast” is correct — “drive fastly” is not a word.
- Some -ly words are adjectives: friendly, lovely, lonely describe nouns (“a friendly dog”).
So -ly is a hint, not a rule.
Good vs well
The classic example. Good is an adjective; well is an adverb.
- “She’s a good writer.” (adjective → writer)
- “She writes well.” (adverb → writes)
- “I’m good” vs “I’m well” — both exist, but “I did well” (not “I did good”) when describing how you performed.
Linking verbs take adjectives
After verbs like be, seem, feel, taste, smell, look, use an adjective, because it describes the subject, not the action:
- “The soup tastes good.” (not “tastes well”)
- “She feels bad.” (not “feels badly”)
Catch the slips
Adjective/adverb mix-ups slip past spell check because both words are spelled correctly. After drafting, run your text through the grammar checker, which understands which form a sentence needs. For the bigger picture of how words function, see our parts of speech guide.
Describe a thing → adjective; describe an action → adverb. Remember good vs well, watch the -ly trap, and these errors disappear.
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