The Semi-colon -- How to Use a Semi-colon

"Hi;" (note the semi-colon).

This drives me crazy. Who uses a semi-colon at the beginning of writing a letter, when everyone knows that it's supposed to be a comma??

But it would not be so bad if this was the only way in which the semi-colon were abused. Unfortunately, the semi-colon takes more abuse than most punctuation marks (which is a shame, really, because it's such a useful punctuation mark!).

There are really only two times you should use a semi-colon:

1. When you have a list of items that has commas within the list, or
2. When you have two related phrases in a sentence which could both be complete sentences, but they are closely related enough to put them into one sentence.

A list of items with commas

There are some instances when you are listing several items that have commas within the list. For example, imagine you are writing about ducks. You want to write about different kinds of ducks in Categories A, B, and C. Let's say that Category A is "ducks from Michigan", Category B is "ducks from Alaska", and Category C is "ducks from Wyoming". Within those three categories, you want to discuss duck colors:

Ducks from Michigan - white, red, and yellow
Ducks from Alaska - blue and red
Ducks from Wyoming - gray, tan, and black

In this case, you will separate the colors with commas, but the broader categories with semi-colons, like so:

This study will consider the white, red, and yellow ducks of Michigan; the blue and red ducks of Alaska; and the gray, tan, and black ducks of Wyoming.

Using commas in between the colors tells the reader that we are listing the colors of one kind of duck; the semi-colon at the end of the state gets the reader ready for another list. Remember that a semi-colon tells the reader to pause a little longer than a comma. Without using a semi-colon, our long list can get very confusing; with a semi-colon, our reader can pause long enough to catch his or her breath, and realize that we're now moving to our next category.

A semi-colon separating two ideas

I once heard the story of an Irish poet who dreamed of a semi-colon just before his death. The significance of this dream? Within a sentence, a semi-colon is used to separate two ideas that are distinct and complete, yet are related.

Did you notice that I used a semi-colon above? I will show you my sentence again:

Without using a semi-colon, our long list can get very confusing; with a semi-colon, our reader can pause long enough to catch his or her breath, and realize that we're now moving to our next category.

The two phrases separated by the semi-colon can each stand alone as a complete sentence, so I could have written it like this:

Without using a semi-colon, our long list can get very confusing. With a semi-colon, our reader can pause long enough to catch his or her breath, and realize that we're now moving to our next Category.

Either of these two methods is grammatically correct. However, in the first version, I tell my reader, "Don't stop yet! There's more related to this same idea", whereas a new sentence can indicate a new idea or even a change of topic.

Is one better than the other? It depends upon what you wish to accomplish. Sometimes, you want your reader to come to an abrupt stop, such as when you are emphasizing a point. At other times, you want the flow of the idea to continue with a pause just long enough to catch your reader's attention.

But please: don't use a semi-colon at the opening of a letter. That's the comma's job.

(Psst, noticed how I used a period instead of a semi-colon in that last sentence? I was trying to emphasize my point!)