A compound sentence connects two independent clauses. (Independent clauses are those which can stand alone as separate sentences.)
Compound sentences often use a coordinating conjunction (for, and, nor, but, or, yet, so) to join the two independent clauses, although a semicolon can be used too.
Sarah went to the shops but Alex stayed at home.
I don't want to get wet so I will take my umbrella.
It was almost midnight yet Kim hadn't finished her homework.
I have a white puppy; her name is Snowy.
The sections of each sentence that are written in blue are independent clauses.
The coordinating conjunction or semicolon (in black) connects them together as one sentence.
A complex sentence connects an independent clause and at least one subordinate clause. (A subordinate clause, also known as a dependent clause, does not form a complete sentence by itself).
Complex sentences often use subordinating conjunctions to join clauses together in one sentence (e.g. after, while, however, if, even though, because, before, until, since).
Since I was passing the postbox, I said I would post the letter.
If I have to tidy up your room one more time, I will scream!
I was determined to eat the dessert even though I felt full.
Casey had forgotten to brush his teeth before he went to bed.
The sections of each sentence that are written in blue are independent clauses.
The sections of each sentence that are written in green are subordinate, or dependent, clauses.
The subordinating conjunction is underlined.
In a complex sentence, either the independent clause or the subordinate clause can be written first:
After they completed their homework, the twins were allowed to watch TV.
If the subordinate clause is first, a comma needs to be placed before the independent clause.
The twins were allowed to watch TV after they completed their homework.
If the independent clause is first, no comma is needed.
