A question often posed by writers is “When should I use semicolons?” The short answer is, Never. Semicolons are most commonly used, wrongly, to introduce lists, definitions and explanations, where the writer should have used a colon. For example:

There are two exceptions to the rule never to use a semicolon: one you must use and one you ought often to avoid if you can.

The first use is simple enough but often abused. In lists, we use a semicolon to separate elements that include commas. You usually use a comma to separate the elements in a list: fish, chips, peas and ketchup (add a comma before the “and” if you are American). But in more complex lists, only a semicolon will do: fish, chips, peas and ketchup; curry and rice; and bananas, apples and carrots. Here, using only commas would create a nightmare of ambiguity, and we don’t want that. However, two things you should avoid: don’t use semicolons when you can just use commas, that is, when the items are not complex; don’t use them when you write your list in bullets or numbered. The latter is common but these days we don’t bother with punctuation in lists because it’s ugly.

The second use puts you in peril of one of writing’s worst crimes: the comma splice. So take care. It’s to divide clauses in a sentence where a comma would be too light. I used one in a sentence in the previous paragraph, where the two clauses form a sort of list, but usually a semicolon separates ideas that are in contrast or complement:

They go high; we go low.

I like her; she hates me.

Now these are at best borderline in today’s English. Close to a comma splice, which is where independent clauses are mistakenly joined with a comma, where you should have used a full stop. For example:

I ran down the road, he saw me and waved.

Ugh.

Remember though that you can join clauses with a comma when the first depends on the second. So this is fine:

When I ran down the road, he saw me and waved.

If you want to get technical, you use a comma because you fronted an adverbial phrase. We’ll talk more about fronting phrases when we look at commas.

Don’t use a semicolon in that instance. People do and it’s always wrong to. Don’t get confused with something like this, which is perfectly fine:

He saw me three times: when I ran down the road; when I swam in the river; when I jumped off the cliff.

You can add an “and” into the last element if you like; in fact, this is one of the few instances when even someone who eschews the Oxford comma might prefer to retain the semicolon. It’s not ambiguous if you take the semicolon out and add “and” but it’s what you might call a “stumble point”. You don’t want a reader to have to look twice at your writing. They should always be able to read through without stumbling over your words (unless they lack vocabulary or you have written something genuinely difficult technically).