Frequency: The word is one of the 700 most common words in English.
1.
You use ~ to introduce a subordinate clause which contains a statement which contrasts with the statement in the main clause.
Although he is known to only a few, his reputation among them is very great...
Although the shooting has stopped for now, the destruction left behind is enormous.
CONJ
2.
You use ~ to introduce a subordinate clause which contains a statement which makes the main clause of the sentence seem surprising or unexpected.
Although I was only six, I can remember seeing it on TV...
= though
CONJ
3.
You use ~ to introduce a subordinate clause which gives some information that is relevant to the main clause but modifies the strength of that statement.
He was in love with her, ~ he did not put that name to it.
= though
CONJ
4.
You use ~ when admitting a fact about something which you regard as less important than a contrasting fact.
Although they’re expensive, they last forever and never go out of style...
CONJ