An adjective is a word or set of words that modifies (i.e., describes) a noun or pronoun. Adjectives may come before the word they modify.

Examples:
That is a cute puppy.
She likes a high school senior.

Adjectives may also follow the word they modify:

Examples:
That puppy looks cute.
The technology is state-of-the-art.

An adverb is a word or set of words that modifies verbs, adjectives, or other adverbs. Adverbs answer how, when, where, why, or to what extent—how often or how much (e.g., daily, completely).

Examples:
He speaks slowly (tells how)
He speaks very slowly (the adverb very tells how slowly)
She arrived today (tells when)
She will arrive in an hour (this adverb phrase tells when)
Let's go outside (tells where)
We looked in the basement (this adverb phrase tells where)
Bernie left to avoid trouble (this adverb phrase tells why)
Jorge works out strenuously (tells to what extent)
Jorge works out whenever possible (this adverb phrase tells to what extent)




Rule 1. Many adverbs end in -ly, but many do not. Generally, if a word can have -ly added to its adjective form, place it there to form an adverb.

Examples:
She thinks quick/quickly.
How does she think? Quickly.

She is a quick/quickly thinker.
Quick is an adjective describing thinker, so no -ly is attached.

She thinks fast/fastly.
Fast answers the question how, so it is an adverb. But fast never has -ly attached to it.

We performed bad/badly.
Badly describes how we performed, so -lyis added.

Rule 2. Adverbs that answer the question howsometimes cause grammatical problems. It can be a challenge to determine if -ly should be attached. Avoid the trap of -ly with linking verbssuch as taste, smell, look, feel, which pertain to the senses. Adverbs are often misplaced in such sentences, which require adjectives instead.

Examples:
Roses smell sweet/sweetly.
Do the roses actively smell with noses? No; in this case, smell is a linking verb—which requires an adjective to modify roses—so no -ly.

The woman looked angry/angrily to us.
Did the woman look with her eyes, or are we describing her appearance? We are describing her appearance (she appeared angry), so no -ly.

The woman looked angry/angrily at the paint splotches.
Here the woman actively looked (used her eyes), so the -ly is added.

She feels bad/badly about the news.
She is not feeling with fingers, so no -ly.