An adverb clause is a dependent clause which takes the place of an adverb in another clause or phrase. An adverb clause answers questions such as "when?", "where?", "why?", "with what goal/result?", and "under what conditions?".

Note how an adverb clause can replace an adverb in the following example:

adverb

The premier gave a speech here.

adverb clause

The premier gave a speech where the workers were striking.

Usually, a subordinating conjunction like "because," "when(ever)," "where(ever)," "since," "after," and "so that," will introduce an adverb clause. Note that a dependent adverb clause can never stand alone as a complete sentence:

independent clause

they left the locker room

dependent adverb clause

after they left the locker room

The first example can easily stand alone as a sentence, but the second cannot -- the reader will ask what happened "after they left the locker room". Here are some more examples of adverb clauses expressing the relationships of cause, effect, space, time, and condition:

cause

Hamlet wanted to kill his uncle because the uncle had murdered Hamlet's father.

The adverb clause answers the question "why?".

effect

Hamlet wanted to kill his uncle so that his father's murder would be avenged.

The adverb clause answers the question "with what goal/result?".

time

After Hamlet's uncle Claudius married Hamlet's mother, Hamlet wanted to kill him.

The adverb clause answers the question "when?". Note the change in word order -- an adverb clause can often appear either before or after the main part of the sentence.

place

Where the whole Danish court was assembled, Hamlet ordered a play in an attempt to prove his uncle's guilt.

The adverb clause answers the question "where?".

condition

If the British co-operate, the Europeans may achieve monetary union.

The adverb clause answers the question "under what conditions?"