The semicolon—sometimes called the love child of the comma and the period—must be an important punctuation mark. After all, the designer of the typewriter keyboard put it on the home row, right under your right pinkie.*
But it isn’t like the period, you know. Everybody knows what to do with a period. You put it at the end of a sentence. Like that. Or you use it with abbreviations, like Dr. or Mr.
What’s the semicolon for? It’s not all that mysterious, really; you use it to join two sentences into a compound sentence. Like that. The beauty of the semicolon is it eliminates the need for a conjunction. In the example I just showed you, I could have joined those two sentences with because: “It’s not all that mysterious, really, because you use it to join two sentences into a compound sentence.”
The semicolon is entirely optional. You can live your whole life without ever using it (and many writers have). There’s no rule that says you have to join two independent sentences together, and even if you decide you want to, there’s no rule that says you have to do it with a semicolon rather than a conjunction.
But I encourage you to experiment with it. Noah Lukeman, in A Dash of Style, says that “The semicolon elevates punctuation from the utilitarian (from punctuation that works) to the luxurious (to punctuation that transcends).” Lynne Truss, author of Eats, Shoots & Leaves, agrees:
The semicolon has been rightly called ” a compliment from the writer to the reader.” And a mighty compliment it is, too. The sub-text of a semicolon is, “Now this is a hint. The elements of this sentence, although grammatically distinct, are actually elements of a single notion. I can make it plainer for you — but hey! You’re a reader! I don’t need to draw you a map!”
Given that using a semicolon implies a level of trust in the reader’s ability to “get it,” you may want to approach it with some trepidation if you’re writing for an ESL audience. Be sure that the connection between the sentence elements is quite clear.
Some recommendations, then:
- Use a semicolon to join two grammatically separate, but thematically linked sentences into a unified whole. “Always try to do things in chronological order; it’s less confusing that way.”
- Use a semicolon before adding a clause introduced by a conjunctive adverb like however, nevertheless, or for example. “Tweedledee was angry at his brother for spoiling his rattle; moreover, he said Tweedledum had poor taste in haberdashery.”
- Some style guides call for semicolons in things like bibliographic citations and indexes (for example, The Chicago Manual of Style indicates that you may need to use them when listing several authors), so if you’re bound by a particular style, be aware of its requirements.
*Actually, the story of the design of the QWERTY keyboard layout is a complicated one; suffice it to say here that much of what people “know” about it is folklore and not hard fact.