Adverb Clauses

It is evident that both the groups of words in italics, in 1 and 2, do the work of an Adverb
as they modify the verb rested, showing when the action was performed.
We at once recognize the first group of words, at sunset, as an Adverb Phrase. Is the
second group of words, when evening came, also-an Adverb Phrase?
No: it is not a Phrase for, unlike a Phrase, it has a Subject (evening) and a Predicate
(came when) of its own, and is thus like a sentence. But though like a sentence it is part
of a sentence.
Such a group of words that forms part of a sentence, and has a Subject and a Predicate of
its own, is called a Clause.
Since the Clause, when evening came, does the work of an Adverb clause.
Def:- An Adverb Clause is a group of words which contains a Subject and a Predicate of
its own, and does the work of an Adverb.