A compound sentence refers to a sentence made up of two independent clauses (or complete sentences) connected to one another with a coordinating conjunction. Coordinating conjunctions are easy to remember if you think of the words "FAN BOYS": The coordinators are as follows: for, and, nor, but, or, yet, so. (Helpful hint: The first letter of each of the coordinators spells FANBOYS.)

Examples of compound sentences include the following:

Joe waited for the train, but the train was late.

I looked for Mary and Samantha at the bus station, but they arrived at the station before noon and left on the bus before I arrived.

Mary and Samantha arrived at the bus station before noon, and they left on the bus before I arrived.

Mary and Samantha left on the bus before I arrived, so I did not see them at the bus station.