Question

What is the definition of a adverb? (This is for my Brother)

Answer 1

A word or phrase that modifies or qualifies an adjective, verb, or other adverb or a word group, expressing a relation of place, time, circumstance, manner, cause, degree, etc. (e.g., gently, quite, then, there ).

Answer 2

An adverb is a word or phrase that modifies or qualifies an adjective, verb, or other adverb. 

Adverbs can express feelings or places and other qualities.

An example would be "Paul is working quickly"

Quickly would be the adverb in that sentence because it is modifying the verb (Working)

Hope this helps!