Adjectives describe nouns — they say what something is. Adverbs describe verbs, adjectives, or other adverbs — they say how something happens or to what degree.
The same root word often appears in both roles. The key is always the same: look at what is being described.
The decision rule
After an action verb, use an adverb. After a linking verb, use an adjective.
Action verbs describe what someone does: run, speak, write, sing. Linking verbs describe what someone is or seems: be, seem, become, appear.
Sensory verbs — look, feel, sound, taste, smell — are linking verbs when they describe the subject itself.
A practical test: replace the verb with a form of be. If the sentence still makes sense, the verb is linking and needs an adjective. The soup is delicious — works. So tastes is linking here.
The linking-verb trap
Some verbs switch between action and linking depending on what you mean. The same sentence with an adjective or an adverb describes two different things.
Look
Feel
Taste
Smell
In each pair, the action meaning takes an adverb and the linking meaning takes an adjective. Context always makes the difference clear.
Good vs well
This is the single most common adjective-adverb confusion in English.
Good is an adjective. Well is its adverb counterpart.
After a linking verb, use good — it describes the subject, not the action.
There is one exception: well is also an adjective when it means healthy.
Both I feel good and I feel well are correct, but they mean slightly different things. I feel good is about mood or general state. I feel well is specifically about health.
Flat adverbs
Some words work as both adjective and adverb without adding -ly. These are called flat adverbs.
| WORD | ADJECTIVE | ADVERB |
|---|---|---|
| fast | a fast train | she runs fast |
| hard | a hard question | he works hard |
| early | an early flight | they arrived early |
| late | a late reply | the bus came late |
| straight | a straight line | drive straight ahead |
| wrong | the wrong answer | you spelled it wrong |
| right | the right direction | turn right at the corner |
| daily | a daily routine | the shop opens daily |
These are not mistakes or informal shortcuts. They are standard English. Adding -ly to some of them either sounds unnatural (fastly does not exist) or changes the meaning entirely.
When -ly changes the meaning
Several common words have both a flat adverb form and a separate -ly form — but the two mean different things.
hard / hardly
late / lately
near / nearly
free / freely
high / highly
deep / deeply
wide / widely
In every pair, the flat form keeps a concrete, physical meaning, while the -ly form shifts to an abstract or figurative one.
Common mistakes
Good vs well
Adjective after an action verb
Adverb after a linking verb
Flat adverb with unnecessary -ly
-ly pairs confused