coordinating conjunction
One of the seven joining words (for, and, nor, but, or, yet, so) that link two grammatically equal elements.
A coordinating conjunction joins two grammatically equal elements — two independent clauses, two words, or two phrases. English has exactly seven — for, and, nor, but, or, yet, so, remembered by the acronym FANBOYS. When one joins two independent clauses, a comma goes before it.
Examples
I wanted to go, but I was tired.