Real Dictionary

subordinate clause
countable noun: A subordinate clause is a clause in a sentence which adds to or completes the information given in the main clause. It cannot usually stand alone as a sentence. Compare main clause.

subordinate clause in American English
dependent clause
noun: a clause that modifies the principal clause or some part of it or that serves a noun function in the principal clause, as when she arrived in the sentence I was there when she arrived or that she has arrived in the sentence I doubt that she has arrived

subordinate clause in British English
noun: a clause with an adjectival, adverbial, or nominal function, rather than one that functions as a separate sentence in its own right