Dependent Words

A clause is a group of words that contains a subject + verb. An independent clause can stand alone as a complete sentence. A clause beginning with a dependent word cannot stand alone but must be embedded in another sentence.

These are the most common dependent words:
"after, than, where, although, that, whether, as though, which, because, unless, whichever, before, until, while, how, what, who(m), if, whatever, whoever, since, when, whose, why"

Here is an independent clause that can stand alone as a complete sentence:
"Marriage is old-fashioned."

Watch what happens when a dependent word introduces this clause:
"although marriage is old-fashioned"

The clause still has a subject and verb, but the addition of the dependent word although makes the clause unable to stand alone. The word although does something else—it prepares the newly dependent clause for embedding in some other sentence:
"{Although* marriage is old-fashioned}, I'm getting married in the morning."

The word although shows the relationship between the two clauses as it embeds one into the other. Other dependent words show different relationships between clauses:
"{Because* marriage is old-fashioned}, I'm going to live without it."
"Cindy is always arguing {that* marriage is old-fashioned}".

Notice the comma in the first sentence, where a dependent clause comes at the beginning of a sentence.

http://www.ccc.commnet.edu/sensen/part1/five/independent.html