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.
[2] An adverbial clause begins with a subordinating conjunction—sometimes called a trigger word.
In the examples below, the adverbial phrase is italicized and the adposition is bolded: Adverbial clauses are divided into several groups according to the actions or senses of their conjunctions: or the paired (correlative) conjunctions: hardly...when, scarcely...when, barely...when, no sooner...than[3] Say when something happens by referring to a period or point of time, or to another event.
We barely had gotten there when mighty Casey struck out.
He spent a lot of money as if he was very rich.