From Manning's Foundations of Statistical Natural Language Processing:
Adverbs modify a verb in the same way that adjectives modify adverb nouns. Adverbs specify place, time, manner or degree:
(3.22) a. She often travels to Las Vegas. b. She allegedly committed perjury. c. She started her career oﬀ very impressively.
Some adverbs, such as often, are not derived from adjectives and lack the suﬃx -ly.
Some adverbs can also modify adjectives ((3.23a) and (3.23b)) and other adverbs (3.23c).
(3.23) a. a very unlikely event b. a shockingly frank exchange c. She started her career oﬀ very impressively.
Certain adverbs like very are specialized to the role of modifying adjectives and adverbs and do not modify verbs. They are called degree degree adverbs adverbs. Their distribution is thus quite distinct from other adverbs, and they are sometimes regarded as a separate part of speech called qualiﬁers.
In English, are adverbs classified into two groups: either modify verbs (not adjectives and adverbs), or modify adjectives and adverbs (not verbs)?