An adverb is a modifying part of speech, targeting anything other than a noun. Not all languages use an adverb to accomplish this, as the role may be filled by other parts of speech, but English uses them widely. Many adverbs in English end with the -ly suffix, usually with an adjective as the root word, as in quickly or obtrusively. This does not always hold true, however, as an adverb does not always use the -ly ending, while some words that are not adverbs end in ly -- smelly and ally are two examples of exceptions. Adverbs are also often formed by taking a noun and adding the -ways or -wise suffix to it, as in the adverbs sideways and contrariwise.

An adverb is often thought of as modifying a verb, both because this is easiest to remember -- due to the name -- and because it is the role most often filled by this part of speech. It is important to note, however, that an adverb may also serve to modify other adverbs, adjectives, and entire clauses or phrases. Usually an adverb serves the purpose of telling when something happened, where it happened, how it happened, how often it happened, or the manner in which it happened. Words or phrases which answer one of these questions are often said to fulfill the adverbial function, whether or not they are truly adverbs.

In the following sentence, for example:

• The bicyclist quickly rode down the hill to the finish line. the adverb quickly is being used to answer the question, In what way did the bicyclist ride down the hill?

There are four main roles an adverb may take on -- as adjective, adverb, verb, or phrasal modifier. Take the following examples:

• The woman laughed heartily.

  The adverb heartily is modifying the verb laughed.

• The gun was barely concealed.

  The adverb barely is modifying the adjective concealed.

• His partner told him he should walk more cautiously in the future.

  The adverb more is modifying another adverb, cautiously, which in turn is modifying the verb walk.

• Sadly, he never listened to her advice.

  The adverb sadly modifies the entire sentence that follows.

There is another use of the adverb, filled by a special set of adverbs known as conjunctive adverbs. These words help to join two clauses in a sentence. Common examples of conjunctive adverbs include: still, meanwhile, then, finally, also, and however. One can usually identify a conjunctive adverb by its use immediately after a semi-colon as a way of joining the two clauses. An example of a sentence using a conjunctive adverb to join two discrete elements is:

It seemed as though time had stopped in anticipation; finally, in a sudden flurry, the storm came.

In modern grammar, there is some discussion of the adverb as a less discrete part of speech than has traditionally been taught. It has been pointed out that adverbs seem to serve such a wide range of functions that lumping them all together may be somewhat disingenuous. Nonetheless, it cannot be denied that the adverb adds an enormous amount to the English language.