Adverbs are words that modify verbs, adjectives or other adverbs, and like adjectives exist in three degrees: positive, comparative and superlative. The positive degree is the form in which an adverb will appear in the dictionary, and usually in a form that ends in -ly. Adverbs, even in the positive degree, can be used in different ways and to perform different types of modification.
Verb Modification
The most basic modification an adverb performs is that found in a standard adverb phrase, or when an adverb modifies a verb to specify how an action was performed, either in manner, frequency, purpose, place or time. In the sentence, "She drove slowly," the adverb "slowly" modifies how she drove. Notice that the phrasing, "She slowly drove" would also be acceptable. An example using a positive-degree adverb that doesn't end in -ly would be the adverb "fast" in the sentence, "She drove fast."
Adjective Modification
Adverbs are also used to modify adjectives, and often specify frequency or intensity. In the sentence, "Her face is really pretty," the adverb "really" modifies the adjective "pretty" by amplifying its intensity. Adverbs can also be used to reduce the intensity of an adjective. It is important to note that not all words that end in -ly are adverbs. for example, the words "lovely," "lonely," and "friendly" are adjectives.
Adverb Modification
Adverbs are also used to modify adjectives, and often specify frequency or intensity. In the sentence, "That sandwich smells really bad," the adverb "really" modifies the adverb "bad" by amplifying its intensity. However, notice that if the word order is altered to, "That sandwich really smells bad," the adverb "really" is no longer altering the adjective "bad," but is now modifying the verb "smells," qualifying that the sandwich really does smell.
Prepositions and Infinitives as Adverbs
Prepositions and infinitive verb phrases can also function as adverbs. In the sentence, "During the movie they sat on the couch," the prepositional phrases "During the movie" and "on the couch" modify the verb "sat' by specifying time and place, respectively. Likewise, in the sentence, "She hurried to catch her ride," the infinitive phrase "to catch" acts as an adverb to modify why she hurried.