Do you dread punctuation? Do you look up how to use colons and semicolons every time you dare to put one in a sentence? It’s OK, we won’t judge. Even grammarians disagree on the rules regarding semicolons and colons. British and American rules are different, and you’ll often find them swapping colons and semicolons. The one common rule: They both show a relationship.
The Relationship? It’s Complicated
It would be nice to have a single, comprehensive rule for using colons and semicolons, but alas, there isn’t one. There are several instances when you might use a colon or a semicolon.
The quickest way to explain colons and semicolons is this: Semicolons show evidence for a statement, while colons create emphasis or give an explanation. Colons also usually show a closer relationship between two clauses. Let’s look at an example of each.
Semicolons
I couldn’t see the road; the fog was too thick.
A semicolon joins together two clauses that could otherwise be separate, complete sentences. Sure, these two sentences could stand alone, but because they're so closely related, it makes sense to join them with a semicolon. It's a stronger pause than what a comma might provide, but it's not a full stop like a period. The word following the semicolon should be lowercase, unless it is a proper noun.
Colons
I had two options: keep driving or stop.
Colons also show relation, but in this case, the colon connects a noun phrase, which shows two examples of the preceding clause. If the words following a colon are a complete sentence, you would capitalize the first word (unlike following a semicolon). If it's not a complete sentence, then keep the first word lowercase.
Lists
Both colons and semicolons have their place in lists, too.
Colons introduce a list.
The note said all students should have the following items on the first day of school: a notebook, pencils, and a ruler.
Meanwhile, semicolons show up in the middle of lists where each item has descriptors attached. Each item on the list already uses commas, so the semicolon punctuation is used to distinguish between the separate items.
Each student was asked to bring a wide-ruled, red notebook; sharpened, new pencils; and a plastic, 12-inch ruler.
When Not To Use Them
Semicolons and colons can’t just be tossed into a sentence whenever you feel like you need to break it up.
When it comes to semicolons, you'll find them between independent clauses. If each part of the sentence can stand on its own as a complete sentence (with a subject and a verb), you can separate them with a semicolon. If one of the phrases doesn’t make a complete sentence, then you might need a comma, an em dash, or even a rephrasing. A semicolon also shouldn’t be used in a list without descriptors where the items can be separated with just a comma.
Colons are a little looser on "when not to use," but they do add an impact to your writing. Be judicious and avoid using them in every sentence, or even paragraph.
It’s OK to get confused with semicolons and colons; you’re not alone. As with most English grammar concepts, there are so many exceptions, alterations, and arguments within the rules that it’s hard to keep them all straight. When in doubt, just leave it out. There’s probably a simpler way to make your point without resorting to advanced-level punctuation.