A subordinating conjunction introduces a subordinate clause. A subordinate clause is not as important as the main clause (independent clause). Subordinating conjunctions show relationships between phrases in a sentence.
The conjunctions before and after tell when.
She took a shower before she went swimming.
She went rock climbing after she went swimming.
The conjunctions because and since tell why.
I did not go swimming because it was raining.
Since Aaliyah missed the bus, Mum drove her to school.
The conjunctions if and unless tell under what condition.
I will go swimming if it is not raining.
Unless it is a snow day, Tuesday will be a regular school day.
Here are a few of the most commonly used subordinating conjunctions.
after just as
as rather than
as if since
as long as so that
as much as than
as soon as that
as though though
even if when
even though whenever
if only whereas
if when wherever
if then whether
in order that while