An adverb is a part of speech. It is any word that modifies any other part of language: verbs, adjectives (including numbers), clauses, sentences and other adverbs, except for nouns; modifiers of nouns are primarily determiners and adjectives.

Adverbs typically answer questions such as how?" (or "in what way?), when?, where?, why? and to what extent?. They often end in -ly.

When they answer how it is usually in what way. When they answer when it is usually a date or a word such as yesterday or today. When they answer why it is usually an explanation of a problem, issue, or situatiuon usually ending after because. When they answer where it usually states a place.

This function is called the adverbial function, and is realized not just by single words (i.e., adverbs) but by adverbial phrases and adverbial clauses.

An adverb as an adverbial may be a sentence element in its own right.

They treated her well. (SUBJECT)

Alternatively, an adverb may be contained within a sentence element.

An extremely attractive woman entered the room. (SUBJECT + ADVERBIAL + OBJECT)

Adverbs in English

In English, adverbs of manner (answering the question how?) are often formed by adding -ly to adjectives. For example, great yields greatly, and beautiful yields beautifully. (Note that some words that end in -ly, such as friendly and lovely, are not adverbs, but adjectives, in which case the root word is usually a noun. There are also underived adjectives that end in -ly, such as holy and ugly.)

The suffix -ly, surprisingly, is related to the Germanic word "lich" meaning corpse or body. (There is also an obsolete English word lych or lich with the same meaning.) Both words are also related to the word like. The connection between -ly and like is easy to understand. The connection to lich is probably that both are descended from an earlier word that meant something like "shape" or "form". In this way -ly in English is cognate with the common German adjective ending -lich and the Dutch ending -lijk. This same process is followed in Romance languages with the ending -mente, -ment, or -mense meaning "of/like the mind".

In some cases, the suffix -wise may be used to derive adverbs from nouns. Historically, -wise competed with a related form -ways and won out against it. In a few words, like sideways, -ways survives; words like clockwise show the transition. Again, it is not a foolproof indicator of a word being an adverb. Some adverbs are formed from nouns or adjectives by appending the prefix a- (such as abreast, astray). There are a number of other suffixes in English that derive adverbs from other word classes, and there are also many adverbs that are not morphologically indicated at all.