An adverbial clause is a dependent clause that functions as an adverb. That is, the entire clause modifies a separate element within a sentence or the sentence itself. As with all clauses, it contains a subject and predicate, though the subject as well as the (predicate) verb are omitted and implied if the clause is reduced to an adverbial phrase as discussed below.

Adverbial clause versus adverbial phrase

Adverbial clauses

An adverbial clause begins with a subordinating conjunction—sometimes called a trigger word. In the examples below, the adverbial clause is italicized and the subordinating conjunction is bolded: According to Sidney Greenbaum and Randolph Quirk (Greenbaum and Quirk, 1990), adverbial clauses function mainly as adverbial adjuncts or disjuncts but differ in syntax from adverbial phrases and adverbial prepositional phrases, as indicated below.

Adverbial phrases

Unlike adverbial clauses, adverbial phrases contain neither an explicit subject nor a predicate. In the examples below, the adverbial phrase is italicized and the adposition is bolded:

Types

Adverbial clauses are divided into several groups according to the actions or senses of their conjunctions: