How to use Semicolons

When it comes to writing, the use of the semicolon always confused me. Many people, myself included, have been under the impression that the semicolon serves the same purpose as a comma; we were wrong.

According to the Writing Resource book, a semicolon should be used to join two related ideas when a coordinating conjunction such as and, but, or, nor, for, so, and yet are not present. Semicolons are most effective when a reader can understand the relationship between both ideas without the help of a "coordinating conjunction".

To make the point a little more clear, consider the following:

Sentence without semicolon:
It rained heavily in the afternoon, but we managed to have our picnic anyway.

Here is the same sentence with the semicolon:
It rained heavily in the afternoon; we managed to have our picnic anyway.

You can also use semicolons to join two independent clauses with a conjunctive adverb such as however, moreover, consequently, thus, nevertheless, and otherwise. Here is an example:

It rained heavily in the afternoon; nevertheless, we managed to have our picnic anyway.

Conjunctive adverbs simply shows the reader how two ideas or clauses are related and help to justify the use of the semicolon.