Semantic features. The adverb is usually defined as a word expressing either property of an action, or property of another property, or circumstances in which an action occurs
Adverbs are commonly divided into qualitative, quantitative and circumstantial.
Qualitative adverbs express immediate, inherently non-graded qualities of actions and other qualities. The typical adverbs of this kind are qualitative adverbs in -ly.
Quantitative adverbs are specific lexical units of semi-functional nature expressing quality measure, or gradational evaluation of qualities.
Circumstantial adverbs are divided into notional and functional.
Just like adjectives, adverbs can be divided into evaluative and specificative, connected with the categorial expression of comparison. Each adverb subject to evaluation grading by degree words expresses the category of comparison. Thus, not only qualitative adverbs are included into the categorial system of comparison.
Morphological features. As to their word-building structure adverbs may be non-derived, or simple and derived We can also distinguish composite forms and phrasal forms of the adverb.
Special mention should be made of preposition-adverb like elements which form a semantic blend with verbs: to give up, to give in, to give out, to give away, to give over, etc; to set up, to set in, to set forth, to set down, etc.; to get on, to get off, to get through, to get about , etc. The verb-adverb combination goes by several names: two-part verbs, composite verbs, phrasal verbs.
These combinations have been treated by different scholars in different ways. Some scholars have treated the second element as a variety of adverbs, as preposition-like, as a special kind of adverb called adverbial postpositon, as postverbial particles, as a special kind of form-word called postpositive, a postfix or postpositive, a separate part of speech called postposition. The great variety of interpretations shows the complexity of the problem. Apparently, the problem requires further research.
Syntactic features. Adverbs are characterized by combinability with verbs, adjectives and words of adverbial nature. The adverb performs the function of an adverbial modifier.