Hey, kids! Last week I wrote up a post on (a bit of) comma usage. This week we’re going to look at both semi-colons and colons. Although these two punctuation marks typically scare people more than commas – maybe because they’re not as everywhere as commas – they have fewer (and more straightforward) uses. So let’s learn about both!
Semi-Colons
Semi-colons can separate the items of a list, like commas can. You may choose to use semi-colons instead of commas because they can provide greater clarity, especially when each item is long or already contains commas.
…skyscrapers and office buildings jostling for space; six-lane roads; tight, cobbled one-way streets; skylanes choked with carpets, broomsticks, and flying horses.
In this example, I chose semi-colons for both reasons! I might’ve used commas to separate a list like “bread, eggs, and cheese.” But in this case, each item in the list is a lot longer than a single word; commas might make it harder to keep track. Additionally, “tight, cobbled one-way streets” and “skylanes choked with carpets, broomsticks, and flying horses” both already contain commas. Separating the items in a list with commas when the items already contain commas makes the list a lot harder to read! Semi-colons make it easier.
Semi-colons can join sentences to form a compound sentence, particularly when the individual sentences are closely related. Unlike commas, semi-colons can do this without the addition of a conjunction! You may choose to use a semi-colon rather than a comma if you decide the sentence will flow better without a conjunction.
Her eyebrows had all but disappeared at this point in her life; she colored them in every morning so she wouldn’t look surprised all the time.
Notice that in this example the two clauses are closely related: Edna colors her eyebrows in every morning because they’ve all but disappeared at this point in her life. Semi-colons often suggest this kind of relationship between clauses.
However, semi-colons can also be used to form compound sentences from less closely related sentences. You can experiment with semi-colons, commas + conjunctions, and periods to find the best flow!
The flying horses whinnied; the aerquestrian shouted in triumph; the police yelled in confusion.
I tend to tire easily of short, punchy sentences (and find they lose their luster when you have a bunch of them in one spot), so for this line I combined them into a compound sentence instead.
Colons
Colons can separate a list from the rest of the sentence. This isn’t strictly necessary, but it can emphasize the list. It might also provide greater clarity for the sentence as a whole – especially if the list is long. If readers might lose track of the clause before the list, you might want to offset the list with a colon! That’s precisely what I chose to do in this example:
She didn’t see the girl at first, only the magical objects littering the tables in front of the altar rail: opal necklaces, bloodstone rings, figures carved from onyx or quartz, heavy spell books with weathered bindings, self-drying coats and gloves of invisibility, daggers with glittering handles and blades inscribed with runes…
The one thing to be aware of in using colons this way is that the clause preceding the colon needs to be a complete sentence. Rather than “Edna saw: opal necklaces…” I’d have to say, “Edna saw the following” or “Edna saw many magical objects: opal necklaces…” A good test for this is to replace the colon with a period. If the clause that comes before the colon now forms a complete thought, you’re good!
Colons can join closely related sentences to form a compound sentence, like semi-colons can. However, unlike semi-colons, sentences joined to form a compound this way must be related! Typically, the sentence that comes after the colon explains, illustrates, or describes the sentence that comes before the colon.
Another thunk of the wizard’s staff and an image appeared in midair: a sword with a glittering, jeweled hilt.
In this example, “a sword with a glittering, jeweled hilt” illustrates or describes the image in the first clause. Notice that while the clause after the colon is a fragment or dependent clause (like our lists above!), the clause before the colon is an independent clause that could stand on its own as a complete sentence.
Edna wasn’t sure how to respond, but it didn’t matter: he was too engrossed in his own fame to pay her any mind.
Here, the clause after the colon explains why Edna’s lack of response doesn’t matter (the professor isn’t paying attention to her anyway).
One more post in the series! Now that we’ve learned the rules governing comma, semi-colon, and colon use, next week we’ll look at reasons you might choose to break them!
Read the whole series on commas, semi-colons, and colons!
e.m.anderson 
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