381. A subordinate clause that serves as an adverbial modifier is called an adverbial clause ([§ 47]).
- Jack spoke {thoughtlessly. | without thinking. | before he thought.}
- The schoolhouse stands {there. | at the crossroads. | where the roads meet.}
- We pay our rent {monthly. | on the first of every month. | when the first of the month comes.}
In each of these groups, the verb (spoke, stands, pay) is modified (1) by an adverb, (2) by an adverbial phrase, (3) by an adverbial clause.
382. Adverbial clauses may be introduced (1) by relative adverbs (when, where, before, etc.); (2) by subordinate conjunctions (if, though, because, etc.); (3) by relative or interrogative pronouns.
383. Adverbial clauses oftenest modify verbs, but they are also common as modifiers of adjectives and adverbs.
- Angry because he had failed, he abandoned the undertaking. [The clause modifies angry.]
- I am uncertain which road I should take. [The clause modifies uncertain.]
- Farther than eye could see extended the waste of tossing waters. [The clause modifies farther.]
- Here, where the cliff was steepest, a low wall protected the path. [The clause modifies here.]
384. An adverbial clause with that may be used to modify verbs and adjectives.
- He rejoiced that the victory was won.
- I am glad that you are coming.
- He was positive that no harm had been done.
- They were unwilling that the case should be brought to trial.
Note. In this use that is equivalent either to “because” or to “as to the fact that.” The clause may be explained as a noun clause in the adverbial objective construction ([§ 109]).
For the classification of adverbial clauses according to their meaning (place, time, cause, concession, etc.), see [pp. 163–182].