In English grammar, an adverbial (abbreviated ) is a word (an adverb) or a group of words (an adverbial clause or adverbial phrase) that modifies or more closely defines the sentence or the verb. (The word adverbial itself is also used as an adjective, meaning "having the same function as an adverb".) Look at the examples below:

The form of adverbials

Adverbials most commonly take the form of adverbs, adverb phrases, temporal noun phrases or prepositional phrases. Many types of adverbials (for instance: reason and condition) are often expressed by clauses. An adverbial is a construction which modifies or describes verbs. When an adverbial modifies a verb, it changes the meaning of that verb. This may be performed by an adverb or a word group, either considered an adverbial: for example, a prepositional phrase, a noun phrase, a finite clause or a non-finite clause.

Types of adverbials that form sentence elements

Adverbials are typically divided into four classes: Adverbial complements (i.e. obligatory adverbial) are adverbials that render a sentence ungrammatical and meaningless if removed. Adjuncts: These are part of the core meaning of the sentence, but if omitted still leave a meaningful sentence. Conjuncts: These link two sentences together. Disjuncts: These make comments on the meaning of the rest of the sentence.

Distinguishing an adverbial from an adjunct

All verb- or sentence-modifying adjuncts are adverbials, but some adverbials are not adjuncts.

Other types of adverbials

Directional and locative particles

Prepositions (in, out, etc.) may be used adverbially to indicate direction or location.

Negators

In some grammar models, negators such as "not" and "never" are considered adverbs with the function of negating adverbial clauses.

Expletives

Often ignored, expletives may take up many adverbial syntactic functions. Pragmatically and semantically, they often serve as intensifiers, boosting the content of the clause they appear in.