Coordinating Conjunctions
A coordinating conjunction is a word that connects two words or two groups of words that are used in the same way—that is, they are the same part of speech or they are grammatically alike. The coordinating conjunctions are and, but, for, nor, or, so, and yet.
Correlative Conjunctions
Correlative conjunctions are always used in pairs. They connect two words or two groups of words that are used in the same way—that is, they are the same part of speech or they are grammatically alike. They include both . . . and; either . . . or; neither . . . nor; not only . . . but; and whether . . . or.
Subordinating Conjunctions
A subordinating conjunction is a word that connects two groups of words that are not used in the same way—that is, they are not the same part of speech and they are not grammatically alike. Some common subordinating conjunctions are after, because, before, how, if, since, than, though, until, when, where, and while. Sometimes a subordinating conjunction comes at the beginning of a sentence. See also: Conjunctions: The Ties That Bind and Subordinating Conjunctions.