Semicolon

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This punctuation mark (;) has two important uses in written English. 

1. It coordinates (separates yet connects evenhandedly) two independent clauses not joined by a coordinating conjunction:
   
                                         I ran to the door; no one was there.
   
   Notice particularly its use when independent clauses are joined by conjunctive adverbs such as however and furthermore. These are not coordinating conjunctions, and therefore a comma is not enough punctuation; a semicolon does the job:
   
                           We were there early; nonetheless, they had already left.
   
   With a coordinating conjunction such as and or but, a comma would serve:
   
                                    We arrived early, but they had already left.
   
   
2. The semicolon also serves to separate clauses or phrases in series constructions when these already contain commas (He had a tall, black horse; a wagon, which someone had given him after the battle; and a threadbare, tattered carpetbag) and elsewhere where there are already other commas.
   
   
3. Another point about the semicolon: the convention is that the semicolon always belongs outside the final quotation marks: He said, “I hit him”; he smiled wickedly.

 

The Columbia Guide to Standard American English. Copyright © 1993 Columbia University Press.