After the first installment of this grammar series, it seemed like there were a lot of people commenting on the usage of semi-colons. And not in a ‘gosh, those semi-colons are confusing little beasts’ way but in more of an ‘I sure love semi-colons; they are the best!’ way. That’s because people who know how to correctly use a semi-colon love to do so; they want to make sure everybody knows of their great skill. And that is because people who know how to correctly use a semi-colon are superior human beings. That’s a fact. A science fact.

Fear not, intrepid writer -- you too can easily learn to wield the semi-colon with confidence, and then you will become more desirable to the mate of your choosing.

We’ve already covered what constitutes a sentence in the lesson on compound sentences. What about when you want to join up two related subject-verb phrases, but you’ve completely used up your supply of conjunctions for the month? Blammo! Semi-colon! See it in action:

Example 1: I wanted to go out for dinner, but Henry said he’d rather stay in.

Example 2: I wanted to go out for dinner; Henry said he’d rather stay in.

You can’t just take out the conjunction (which is but in Example 1) and leave the comma. A comma alone is not powerful enough to separate two sentences! I see that error very often, and it’s wrong. Two sentences and no conjunction requires a semi-colon.

The key to using a semi-colon appropriately is choosing sentences that could stand apart from one another but which are related in theme. In the above example, both sentences have to do with dinner plans. This usage makes much less sense:

I’m writing a post on grammar; I was five when I got my first pet cat.

Sure, they’re both about me, but there’s just no call for a semi-colon. However, I can say, I’m writing a post on grammar; it’s something about which I can be slightly pedantic. You can see the relationship between those two ideas, right?

Often, writers use semi-colons to avoid lulling their audience to sleep with the constant rhythm of compound sentences. Or the similar, tedious clack-clack-clack that a string of simple sentences can achieve. This is something we should all try to avoid; knowledge of different sentence constructions leads to more interesting writing.

Other times, you’ll just want to join up two related sentences (either for clarity or, again, for the sake of rhythm) that wouldn’t make sense with a conjunction. I’m writing a post on grammar; it’s something about which I can be slightly pedantic. is a good example of this. I would struggle to link those two sentences with a conjunction (and have it not sound silly), but having them stand alone with a full stop between would be jarring.

So, to review: there should be a complete subject-verb sentence on either side of a semi-colon, and the sentences in question should have a logical connection. I sometimes see writers get tripped up when it comes to choosing between semi-colons and full-blown colons, but that will have to be a topic for another post.