An adverb is a word or an expression that modifies a verb, adjective, another adverb, determiner, clause, preposition, or sentence. Adverbs typically express manner, place, time, frequency, degree, level of certainty, etc., answering questions such as how?, in what way?, when?, where?, and to what extent?. This is called the adverbial function, and may be performed by single words (adverbs) or by multi-word adverbial phrases and adverbial clauses.
Adverbs are traditionally regarded as one of the parts of speech. Modern linguists note that the term "adverb" has come to be used as a kind of "catch-all" category, used to classify words with various types of syntactic behavior, not necessarily having much in common except that they do not fit into any of the other available categories (noun, adjective, preposition, etc.)
The English word adverb derives (through French) from Latin adverbium, from ad- ("to"), verbum ("word", "verb"), and the nominal suffix -ium. The term implies that the principal function of adverbs is to act as modifiers of verbs or verb phrases. An adverb used in this way may provide information about the manner, place, time, frequency, certainty, or other circumstances of the activity denoted by the verb or verb phrase. Some examples:
Adverbs can also be used as modifiers of adjectives, and of other adverbs, often to indicate degree. Examples:
Adverbs thus perform a wide range of modifying functions. The major exception is the function of modifier of nouns, which is performed instead by adjectives (compare she sang loudly with her loud singing disturbed me; here the verb sang is modified by the adverb loudly, whereas the noun singing is modified by the adjective loud). However, because some adverbs and adjectives are homonyms, their respective functions are sometimes conflated:
The word "even" in the first sentence is an adjective, since it is a prepositive modifier that modifies the noun "numbers". The word "even" in the second sentence is a prepositive adverb that modifies the verb "drank."
Although it is possible for an adverb to precede or to follow a noun or a noun phrase, the adverb nonetheless does not modify either in such cases, as in:
In the first sentence, "Internationally" is a prepositive adverb that modifies the clause, "there is ..." In the second sentence, "internationally" is a postpositive adverb that modifies the clause, "There is ..." By contrast, the third sentence contains "international" as a prepositive adjective that modifies the noun, "shortage."
Adverbs can sometimes be used as predicative expressions; in English, this applies especially to adverbs of location:
In English, adverbs of manner (answering the question how?) are often formed by adding -ly to adjectives, but flat adverbs (such as in drive fast, drive slow, and drive friendly) have the same form as the corresponding adjective. Other languages often have similar methods for deriving adverbs from adjectives (French, for example, uses the suffix -ment), or else use the same form for both adjectives and adverbs, as in German and Dutch, where for example schnell or snel, respectively, mean either "quick" or "quickly" depending on the context. Many other adverbs, however, are not related to adjectives in this way; they may be derived from other words or phrases, or may be single morphemes. Examples of such adverbs in English include here, there, together, yesterday, aboard, very, almost, etc.
Where the meaning permits, adverbs may undergo comparison, taking comparative and superlative forms. In English this is usually done by adding more and most before the adverb (more slowly, most slowly), although there are a few adverbs that take inflected forms, such as well, for which better and best are used.
For more information about the formation and use of adverbs in English, see English grammar § Adverbs. For other languages, see § In specific languages below, and the articles on individual languages and their grammars.
Adverbs are considered a part of speech in traditional English grammar, and are still included as a part of speech in grammar taught in schools and used in dictionaries. However, modern grammarians recognize that words traditionally grouped together as adverbs serve a number of different functions. Some describe adverbs as a "catch-all" category that includes all words that do not belong to one of the other parts of speech.
A logical approach to dividing words into classes relies on recognizing which words can be used in a certain context. For example, the only type of word that can be inserted in the following template to form a grammatical sentence is a noun:
When this approach is taken, it is seen that adverbs fall into a number of different categories. For example, some adverbs can be used to modify an entire sentence, whereas others cannot. Even when a sentential adverb has other functions, the meaning is often not the same. For example, in the sentences She gave birth naturally and Naturally, she gave birth, the word naturally has different meanings: in the first sentence, as a verb-modifying adverb, it means "in a natural manner", while in the second sentence, as a sentential adverb, it means something like "of course".
Words like very afford another example. We can say Perry is very fast, but not Perry very won the race. These words can modify adjectives but not verbs. On the other hand, there are words like here and there that cannot modify adjectives. We can say The sock looks good there but not It is a there beautiful sock. The fact that many adverbs can be used in more than one of these functions can confuse the issue, and it may seem like splitting hairs to say that a single adverb is really two or more words that serve different functions. However, this distinction can be useful, especially when considering adverbs like naturally that have different meanings in their different functions. Rodney Huddleston distinguishes between a word and a lexicogrammatical-word.
Grammarians find difficulty categorizing negating words, such as the English not. Although traditionally listed as an adverb, this word does not behave grammatically like any other, and it probably should be placed in a class of its own.