Semicolons and colons 101

My very first post on Red Pens and Playwriting was about semicolons: unironically my favourite punctuation. To wrap up my use of Grammar Talk posts to promote my new writing guide Red Pens 101, what could be better than going back to the beginning? I have not deviated much from my original guidance about semicolons, but the new guide includes colons in the same section, which have not been covered on the blog before. Yay, new stuff! In short, the following content is taken directly from Red Pens 101—if you want more like it, you can purchase the guide from my Ko-Fi shop.

Semicolons are my single favourite piece of punctuation. They're also one of the most mysterious; perhaps that's why I like them so much! Seriously, though, there are a lot of people who view semicolons with a level of suspicion because they're not sure how to use them. The regular colon is, fortunately, less mysterious, but does also have very specific jobs.

Semicolons

In order to understand semicolons, you first need to understand clauses. As I have discussed in previous posts, a clause can be either dependent or independent: an independent clause is one that can stand as its own sentence grammatically, whereas a dependent clause cannot.

Now, if you're sticking a dependent clause to an independent clause, you'll most likely want to use a comma, or nothing at all:

Although the radio says otherwise, there's a storm coming.

I'm going to tie down the trampoline in case the wind picks up.

But if you've got two independent clauses that you want to join together, a comma is just not going to cut it. In this case, you need the added strength of a semicolon to avoid the horrors of a run-on sentence:

There's a storm coming; I'm going to tie down the trampoline.

Although the radio says otherwise, there's a storm coming; I'm going to tie down the trampoline in case the wind picks up.

Another way to think of it is that a semicolon is used grammatically in the same places you might use a full stop (or "period", for my American friends). So you could avoid semicolons altogether by simply separating all of your independent clauses into their own sentences, and everyone's happy. Alternatively, as we've discussed, you could use an em-dash or a conjunction instead of a semicolon. The reason semicolons are useful, however, is that they imply a relationship between the clauses on either side, which might affect how your sentences are read. Compare the effect of the following examples:

The sun beat down, making me sweat; I squirmed uncomfortably. Moira was glaring daggers in my direction.

The sun beat down, making me sweat. I squirmed uncomfortably; Moira was glaring daggers in my direction.

The sun beat down, making me sweat. I squirmed uncomfortably. Moira was glaring daggers in my direction.

As you can see, there's some subtle cause and effect being communicated by the use of semicolons that would have to be spelled out otherwise. Why is the narrator squirming? Is it the hot sun that's to blame, or Moira's displeasure? Admittedly, an em-dash could accomplish this too, but the semicolon is both more formal and less abrupt, so if you're concerned about the flow or tone of your writing it's important to have both options available.

There's one other place where you may commonly see semicolons, and that's as part of a list where commas are included within at least one item, so the mighty semicolon is brought in to divide the items in way that makes the list more readable. For example:

We drove through Tallahassee, Florida; Atlanta, Georgia; St Louis, Missouri; Lansing, Michigan, in a detour that surprised us all; and finally, at the end of it all, Indianapolis, Indiana.

In this usage, the semicolon takes the place of the commas that would normally separate the items in the list, including the Oxford comma if relevant.

Colons

In the world of punctuation (as opposed to anatomy), colons are used primarily to introduce things such as lists, clarifications, quotes and examples, or definitions.

The number of chores grew and grew: putting out the laundry, vacuuming the carpets, dusting the knick-knacks, washing the dishes, and weeding the garden.

There was only one thing Frances could do in this situation: she pulled the fire alarm.

I made the best-looking pie of the day: it had a lattice design wreathed in vines, and a cluster or pastry roses in the corner.

It's like Shakespeare said: all the world's a stage.

One of my favourite words is "defenestrate": the act of throwing something (or someone) out of a window.

Colons are also used to connect titles with subtitles (Inventing the Renaissance: The Myth of a Golden Age) or to indicate a verse number in texts with numbered verses (John 3:16). You might also commonly see them used to represent time (3:30 am), though this is regional; in some parts of the world it's more appropriate to use a full stop here (3.30 am). They are also frequently used in dialogue-based texts like scripts and screenplays to label who is speaking which lines, though this is also not universal as particular publishing and formatting styles may use other means to indicate this.