Here are a few more guidelines for punctuating sentences, offered in response to comments on my How to punctuate a sentence post.
A reader asked when it’s appropriate to join sentences with a semi-colon. The semi-colon is a good choice when sentences are clearly related, when they seem to go together, when a period would create an overly emphatic stop between sentences. Alas, there’s no rule to determine whether sentences are related in a way that makes a semi-colon a good choice. Making this decision seems to me a matter of acquired intuition.
The presence of a connecting word or phrase (such as nevertheless, therefore, thus, even so, in contrast) is a good sign that you’re in semi-colon territory. But longish sentences, even if they’re clearly related, are likely to be easier for a reader to take in if they’re separated by a period.
One caution: it’s easy to overuse the semi-colon. As an undergraduate, I often used semi-colons indiscriminately; I joined sentences together in long, unwieldy chains; my excitement about tying ideas together carried me away; as you can see in this example, the result is not reader-friendly.
Horst Grundkenfelder’s comment added a helpful detail about semi-colon use: when one or more commas appear within items in a series, semi-colons should separate the items. Monty Python makes it easy to illustrate this point:
The menu offered limited choices: egg and bacon; egg, sausage, and bacon; egg and Spam; egg, bacon, and Spam; and egg, bacon, sausage, and Spam.
Two readers asked about the dash. It’s a very useful element of punctuation, as it allows for greater condensation in the presentation of ideas. The dash is appropriate in setting off an element that strongly interrupts the movement of a sentence. For instance:
Emily Dickinson and Walt Whitman — the one oblique and elliptical, the other expansive and declamatory — might be said to have invented modern American poetry.
Three instruments — clarinet, trumpet, and muted trombone — create the unusual tone colors of Duke Ellington’s “Mood Indigo.”
My examples with items in a series (“wine, women, and song”) all included a comma before and, the so-called serial comma or Oxford comma. I’m aware of course that opinions differ on that final comma’s necessity. Keeping that comma seems to me the better choice, simplifying, in one small way, the problems of punctuation. If you always put the comma in, you avoid problems with ambiguous or tricky sentences in which the comma’s absence might blur the meaning of your words.
Wikipedia has a lengthy article on the serial comma, giving arguments for and against. And Shaine Mata, who, like me, likes the serial comma, has invented some wonderful examples to argue for its use: A Lesson on Commas in a Series.
The most important thing to remember about punctuation: it’s a matter of conventions, shared agreements that help bring clarity to written communication. If you don’t agree this sentence unpunctuated difficult to read can serve as a last attempt to persuade. If you do agree, that last sentence — unpunctuated, difficult to read — can serve to confirm what you already understand.
Michael Leddy teaches college English and blogs at Orange Crate Art.