http://www.grammarbook.com/punctuation/semicolons.asp
Even Oxford educated people can forget the rules of grammar,just like nearly everyone else in the UK.In fact, if you are too good at grammar it might make you bad at it in a very real sense, at this moment in time.I hope you can grasp what I write and use it for something or other,like, er,what d’you call it?
It’s no accident that a semicolon is a period atop a comma. Like commas, semicolons indicate an audible pause—slightly longer than a comma’s, but short of a period’s full stop.
Semicolons have other functions, too. But first, a caveat: avoid the common mistake of using a semicolon to replace a colon (see the “Colons” section).
Incorrect: I have one goal; to find her.
Correct: I have one goal: to find her.
Rule 1a. A semicolon can replace a period if the writer wishes to narrow the gap between two closely linked sentences.
Examples:
Call me tomorrow; you can give me an answer then.
We have paid our dues; we expect all the privileges listed in the contract.
Rule 1b. Avoid a semicolon when a dependent clause comes before an independent clause.
Incorrect: Although they tried; they failed.
Correct: Although they tried, they failed.
How my heart sings 