In linguistics, an adverbial phrase ("AdvP") is a multi-word expression operating adverbially: its syntactic function is to modify other expressions, including verbs, adjectives, adverbs, adverbials, and sentences. Adverbial phrases can be divided into two types: complement adverbs and modifier adverbs. For example, in the sentence She sang very well, the expression very well is an adverbial phrase, as it modifies the verb to sing. More specifically, the adverbial phrase very well contains two adverbs, very and well: while well modifies the verb to convey information about the manner of singing (for example, She sang well versus She sang badly), very is a degree modifier that conveys information about the degree to which the action of singing well was accomplished (for example, Not only did she sing well, she sang very well).
Types
The following examples illustrate some of the most common types of adverbial phrases. All adverbial phrases appear in bold; when relevant, the head of each adverbial phrase appears in square brackets.
Degree adverbial phrases
The heads of each of the following adverbial phrases are degree adverbials (written "Deg" in syntactic trees). Degree adverbials modify adjacent adverbs (that is, an adverb that is lower in the syntactic tree than the degree adverbial). Degree adverbials are commonly used in English to convey the intensity, degree, or focusing of an adjacent adverb. In most cases, a degree adverbial is used to modify an adverb in an adverbial phrase: for example, in (1) the degree adverbial very modifies the adverb quickly; in (2) the degree adverbial extremely modifies the adverb hard; in (3) the degree adverbial really modifies the adverb well; and in (4), the degree adverbial so modifies the adverb soon.
(1) They repaired my car [very] quickly. (2) He worked [extremely] hard in the game. (3) She did [really] well in her race. (4) Why are you leaving [so] soon?
Modifier adverbial phrases
Modifier adverbial phrases combine with a sentence, and the removal of the adverbial phrase yields a well-formed sentence. For example, in (5) the modifier adverbial phrase in an hour can be removed, and the sentence remains well-formed (e.g., I'll go to bed); in (6) the modifier AdvP three hours late can be omitted, and the sentence remains well-formed (e.g., We arrived); and in (7), the modifier AdvP later in the day can be omitted, and the sentence remains well-formed (e.g. The situation had resolved). Just as adjective phrases function attributively to give additional information about an adjacent noun, the modifier adverbial phrases illustrated in (5) to (7) function as secondary predicates that give additional temporal information about the sentence.
(5) I'll go to bed in an hour. (6) We arrived three hours late. (7) Later in the day the situation had resolved.
Complement adverbial phrases
Complement adverbial phrases are much less common than their modifier counterparts. Adverbial phrases functioning as complements usually arise when an adverb licenses a complement as a selectional requirement. Nearly all of these complements license an adjoining prepositional phrase. Below are a few examples of complement adverbial phrases.
(8) Purchase of State vehicles is handled [similarly] to all State purchases. (9) Foreign firms in US markets are treated [equally] with their US counterparts.
Distinguishing adverbs, adverbial phrases, and adverbial clauses
The following sentences illustrate the difference between adverbs, adverbial phrases, and adverbial clauses. (10) I'll go to bed soon. (11) I'll go to bed in an hour. (12) I'll go to bed when I've finished my book. In the first example, "soon" is an adverb (as distinct from a noun or a verb), which is a type of adverbial. In the second sentence, the modifier "in an hour" has the same syntactic function (that is, to act adverbially and modify the base of the sentence "I'll go to bed"), though it does not contain an adverb. This modifier consists of a preposition and a determiner phrase, and functions as an adverbial, thus making it an adverbial phrase. In the third example, we see a whole clause functioning as an adverbial; it is termed an adverbial clause.
Distribution
Functionally, the term adverbial refers to all structures that can take the position of an adverb on a phrase structure level. Adverbs modify the functional categories that occur in a sentence and may also be treated as predicates which are functionally open and require one or more arguments to be satisfied. It has been argued that the distribution of adverbs is largely conditioned by their lexical nature or thematic properties.