A subordinate clause is the same thing as a dependent clause. We call it a subordinate clause because it is not as important as the independent clause. We call it a dependent clause because it is dependent on the independent clause. We can use the terms subordinate clause and dependent clause interchangeably.
A subordinate clause always begins with a subordinating conjunction. Here are some common subordinating conjunctions: after, as soon as, because, before, if, since, when, while, until
Each subordinating conjunction begins a subordinate clause. Here are some subordinate clauses. Notice how they are not complete sentences.
After we eat dinner
As soon as I finish painting
Because the dog ran away
Before you throw that in the trash
If it rains tomorrow
Since we talked last week
When the bus arrives
Until you get your homework finished
Each of these subordinate clauses feels unfinished. It seems like we need more information in the sentence. That is why a subordinate clause is dependent. The subordinate clause cannot stand on its own. It must be attached to an independent clause to make a complete sentence.
Whenever you begin a sentence with a subordinating conjunction, you are writing a subordinate clause. You must add an independent clause to make a complete sentence.
▶It’s your turn. Find the subordinating conjunction in this complete sentence. I will dry the dishes while you do your homework. This complete sentence has an independent clause followed by a subordinate clause. Did you find the subordinating conjunction at the start of the dependent clause? Good for you!