An adverb is a word that modifies a verb, adjective, or other adverb and provides information about when, where, how, or to what extent an action occurs. Many adverbs are formed by adding "-ly" to an adjective. Adverbs can describe when an action happens, such as "yesterday" or "soon", or how an action is performed, such as "kindly", "strangely", "sadly", "safely", "happily", or "slowly". Learning to use adverbs can make writing more descriptive and interesting.