Use an adjective when you describe a noun or pronoun. Use an adverb when you describe a verb, adjective, another adverb, phrase, clause, or sentence. The right choice depends on what the word is describing, not only on how the word looks.
Main Answer
The simple test is this: if the word describes a person, place, thing, or idea, it is usually an adjective. If it describes how, when, where, how often, or to what degree something happens, it is usually an adverb.
Table of Contents
Adjective vs Adverb: Which One Is Correct?
Both adjectives and adverbs are correct English word types. The mistake happens when one is used in the other’s job.
- Adjective: describes a noun or pronoun. Example: a quiet room.
- Adverb: describes a verb, adjective, another adverb, phrase, clause, or sentence. Example: She spoke quietly.
Cambridge Grammar describes adjectives as words that give more information about people and things, while adverbs can show time, place, manner, degree, or frequency. Source-1✅
Memory trick: an adjective tells you what kind of thing. An adverb tells you how, when, where, how often, or how much.
The Main Difference Between an Adjective and an Adverb
The difference is about function. A word can look simple, but its job in the sentence decides whether it works as an adjective or an adverb.
Adjective Job
An adjective gives information about a noun or pronoun.
- a soft pillow
- the red bag
- She looks happy.
Adverb Job
An adverb gives information about an action, quality, degree, or whole statement.
- walk slowly
- very bright
- She answered politely.
How To Choose the Correct Word
Ask one clean question: What is this word describing? That usually gives the answer.
Use an Adjective When the Word Describes a Noun
- ✓ Correct It was a slow train.
- ✕ Wrong It was a slowly train.
Train is a noun. The word slow describes the train, so the adjective is correct.
Use an Adverb When the Word Describes an Action
- ✓ Correct The train moved slowly.
- ✕ Wrong The train moved slow.
Moved is a verb. The word slowly describes how the train moved, so the adverb is correct.
Adjectives After Linking Verbs
Some verbs do not show a normal action. They connect the subject to a description. These are often called linking verbs. Common examples include be, seem, look, feel, smell, taste, sound, become.
After a linking verb, English often uses an adjective, not an adverb, because the word describes the subject.
- ✓ Correct The soup tastes good.
- ✕ Wrong The soup tastes well.
- ✓ Correct He feels bad.
- ✕ Wrong He feels badly.
In The soup tastes good, good describes the soup. In He feels bad, bad describes his state. Merriam-Webster notes that an adjective can come after linking verbs such as be or seem. Source-2✅
Words Ending in -ly Are Not Always Adverbs
Many adverbs end in -ly, but that pattern is not a perfect rule. Some adjectives also end in -ly, such as friendly, lovely, lonely, lively, silly, ugly.
- ✓ Correct She is a friendly person.
- ✕ Wrong She smiled friendly.
- ✓ Better She smiled in a friendly way.
Cambridge Grammar explains that many adverbs are formed from an adjective plus -ly, but it also notes same-form adjective/adverb words such as fast, hard, and late. Source-3✅
Adjective vs Adverb Examples Table
| Meaning Needed | Correct Adjective Use | Correct Adverb Use | What Changes? |
|---|---|---|---|
| Speed | a slow walk | walk slowly | The adjective describes the walk as a thing; the adverb describes the action. |
| Care | a careful writer | write carefully | The adjective describes the person; the adverb describes how the person writes. |
| Noise | a loud voice | speak loudly | The adjective describes the voice; the adverb describes speaking. |
| Quality | a good answer | answer well | Good is usually the adjective; well is often the adverb. |
| Emotion or State | She feels sad. | She spoke sadly. | After feels, the adjective describes the subject. After spoke, the adverb describes the action. |
| Degree | a very small room | work very quickly | Very can modify an adjective or another adverb. |
Words That Can Be Both Adjectives and Adverbs
Some English words keep the same form as an adjective and an adverb. This is why adding -ly is not always right.
- Fast
- ✓ Correct That is a fast car. / The car moves fast.
- Hard
- ✓ Correct That was a hard test. / She worked hard.
- Late
- ✓ Correct The late train arrived. / The train arrived late.
- Daily
- ✓ Correct a daily habit / We practice daily.
Merriam-Webster explains that adverbs can modify verbs, adjectives, other adverbs, phrases, or full sentences, and it also lists common adverbs that do not end in -ly, including often, soon, today, too, very, and well. Source-4✅
Common Adjective and Adverb Errors
Most mistakes come from choosing the word by sound instead of by sentence job. These are the patterns that cause the most confusion.
Good vs Well
- ✓ Correct She is a good singer.
- ✓ Correct She sings well.
- ✓ Correct I feel good.
Good is usually an adjective. Well is often an adverb, but it can also work as an adjective when it means healthy. Example: I am well.
Bad vs Badly
- ✓ Correct I feel bad.
- ✓ Correct The machine works badly.
- ✕ Wrong I feel badly.
I feel bad means your state is bad. I feel badly can sound like your sense of touch is not working well, so it is not the normal choice for mood or condition.
Real vs Really
- ✓ Correct That is a real problem.
- ✓ Correct That is really difficult.
- ✕ Wrong That is real difficult.
Real describes a noun: a real problem. Really can describe an adjective: really difficult.
Slow vs Slowly
- ✓ Correct Please drive slowly.
- ✓ Correct This is a slow road.
Slowly describes the action drive. Slow describes the noun road.
A Simple Sentence Test
Use this short check when you are unsure:
- Find the word being described.
- Ask whether that word is a noun, pronoun, verb, adjective, or adverb.
- Use an adjective for nouns and pronouns.
- Use an adverb for verbs, adjectives, other adverbs, phrases, clauses, and sentence meaning.
Example Test
Sentence: He gave a clear / clearly answer.
Word described: answer
Answer is a noun, so the adjective is correct.
✓ Correct He gave a clear answer.
Another Example Test
Sentence: He answered clear / clearly.
Word described: answered
Answered is a verb, so the adverb is correct.
✓ Correct He answered clearly.
FAQ
Is It an Adjective or an Adverb?
It depends on what the word describes. If it describes a noun or pronoun, it is an adjective. If it describes a verb, adjective, another adverb, phrase, clause, or sentence, it is an adverb.
Is “Fast” an Adjective or an Adverb?
Fast can be both. In a fast car, it is an adjective. In The car moves fast, it is an adverb.
Is “Friendly” an Adjective or an Adverb?
Friendly is usually an adjective. Say a friendly person. For an adverb meaning, use in a friendly way: She spoke in a friendly way.
Should I Say “I Feel Bad” or “I Feel Badly”?
Say I feel bad when you mean your mood, condition, or feeling is bad. Bad works as an adjective after the linking verb feel.
Are All Words Ending in -ly Adverbs?
No. Many adverbs end in -ly, but some adjectives also end in -ly, including friendly, lovely, lonely, lively, and ugly.
What Is the Easiest Way To Tell the Difference?
Find the word being described. If the described word is a noun or pronoun, choose the adjective. If it is an action or another describing word, choose the adverb.