What is an Adverb Clause?
"He saw Mary when he was in New York" and "They studied hard because they had a test" are adverb clauses. Adverb clauses express when, why, opposition and conditions and are dependent clauses. This means that an adverb clause can not stand by itself - in other words, "When he went to New York." is not a complete sentence. It needs to be completed by an independent clause. Example: He went to the Guggenheim museum when he was in New York.
Punctuation
When an adverb clause begins the sentence, use a comma to separate the two clauses. Example: As soon as he arrives, we will have some lunch.. When the adverb clause finishes the sentence there is no need for a comma. Example: He gave me a call when he arrived in town.
For more information about how to use these words click on the link for an explanation of the usage.
List of Words (subordinating conjunctions) Introducing Adverb Clauses
TIME
after, before, when, while, as, by the time (that), as soon as, since, until, whenever, the first time (that), the next time (that), the last time (that), every time (that) - more information on adverb clauses with time expressions
CAUSE AND EFFECT
because, since, as, as long as, so long as, due to the fact that - more information on adverb clauses with expressions of cause and effect
OPPOSITION
although, even though, though, whereas, while - more information on adverb clauses with expressions of opposition
CONDITION
if, only if, unless, whether (or not), even if, providing (that), in case (that), provided (that), in the event (that) - more information on adverb clauses with condition expressions

