There are two kinds of clauses -- independent, and dependent.
A dependent clause has a subject and a verb just like an independent
clause, but it can't stand alone because it begins with a dependent word such as:
after since where
although so whereas
as so that wherever
as if than whether
because that which
before though whichever
even if unless while
even though until who
how whatever whose
if when why
in order that whenever
Whenever a clause begins with one of the dependent words (unless it's a
question, which would never give you any trouble), it is dependent. If we take an
independent clause such as
We finished the game.and put one of the dependent words in front of it, it becomes dependent:
After we finished the game
Although we finished the game
As we finished the game
Before we finished the game
If we finished the game
Since we finished the game
The we finished the game
When we finished the game
While we finished the gameThe clause can no longer stand alone. As you read it, you can hear that it doesn't
make a complete statement. It leaves the reader expecting something more. It's a
fragment and must be punctuated as a sentence. To correct such a fragment, simply add
an independent clause:
After we finished the game, we went to the clubhouse.
We went to the clubhouse after we finished the game.
We were happy that we finished the game early.
While we finished the game, the others waited.
(not mine -- but poasted by me -- Father Luke)
Writers' Resources 
