Compound

Use a comma before a coordinating conjunction that connects two independent clauses.

Independent clause, coordinating conjunction independent clause.

Independent clause, for independent clause.
Independent clause, and independent clause.
Independent clause, nor independent clause.
Independent clause, but independent clause.
Independent clause, or independent clause.
Independent clause, yet independent clause.
Independent clause, so independent clause.

Use a semicolon to connect two closely related or parallel independent clauses.

Independent clause; independent clause.

Use a semicolon before and a comma after a transition that connects two independent clauses. If the transition is short, the comma may not be necessary.

Independent clause; consequently, independent clause.
Independent clause; further, independent clause.
Independent clause; however, independent clause.
Independent clause; indeed, independent clause.
Independent clause; therefore, independent clause.
Independent clause; nevertheless, independent clause.
Independent clause; then independent clause.

Complex

The placement of a subordinate clause determines the punctuation of the clause.
Use a comma following an introductory subordinate clause to separate it from the independent clause.

After subordinate clause, independent clause.
Although subordinate clause, independent clause.
Because subordinate clause, independent clause.
If subordinate clause, independent clause.
Until subordinate clause, independent clause.
Whereas subordinate clause, independent clause.
While subordinate clause, independent clause.

When the subordinate clause follows the independent clause, no comma is needed unless the clause expresses contrast or exception (although, while, whereas).

 

Learn more about "Compound Sentences."

Learn more about "Complex Sentences."