Semicolon - a punctuation mark used primarily to connect independent clauses within a sentence.
We have all used a semicolon to make our writing look fancy. We have also, more than likely, had the nagging feeling that we weren't using it correctly. Perhaps we had heard that a semicolon was a "bigger comma", or that it was somewhere between a comma and a full stop.
While these explanations are not entirely incorrect, there is more to the story. So, let's set the record straight regarding the correct usage of the semicolon.
If a sentence contains two independent clauses that are separated by a coordinating conjunction, we can replace the coordinating conjunction with a semicolon.
With a coordinating conjunction
I'm going for a walk, but I'll return before dinner.
He arrived in the town at six, and the sun was setting.
With a semicolon
I'm going for a walk; I'll return before dinner.
He arrived in the town at six; the sun was setting.
If two independent clauses are linked by a conjunctive adverb, a semicolon should be placed before the conjunctive adverb.
Examples
The semicolon connects ideas in an elegant fashion; however, it is often misused
Most people don't understand the semicolon; therefore, it is worth learning how it works.
While a comma is used to separate items in a list, what happens if the items in the list already contain commas?
Semicolon to the rescue:
Example
Each shelf in my record collection contains a number of genres: the bottom shelf has blues, rock and hip hop; the middle has jazz, reggae and metal; and the top shelf has electronic, classical and world music.