I. Adjective Clauses
II. Adverbial Clauses

396. Adjective clauses of place and time may be introduced by relative pronouns (see examples above).

Adjective and adverbial clauses of place and time may be introduced by relative adverbs. Thus,—

For as and since in causal clauses, see [§ 398]; for while in concessive clauses, see [§ 399].

397. Clauses of time are sometimes shortened by the omission of the copula and its subject.