Adjectives and adverbs frequently add indispensable differences in meaning to the words they modify (describe). In basketball, for example, there is an important difference between a flagrant foul and a technical foul, a layup and a reverse layup, and an angry coach and an abusively angry coach. In each instance, the modifiers are crucial to accurate communication.

Adjectives modify nouns and pronouns; they answer the questions which? how many? and what kind? Adverbs modify verbs, adjectives, and other adverbs; they answer the questions how? when? where? and to what extent? Many adverbs are formed by adding -ly to adjectives (slight, slightly), but some are formed in other ways (outdoors) or have forms of their own (very).