Introduction to Punctuation


Many of us have a conflicted attitude towards punctuation. On social media, we tend to enjoy it when friends share humorous pictures of punctuation mistakes. But when it comes to actually studying the rules of grammar, we can be a bit lazy. Intuitively we feel that we know the rules, but most of us end up guessing where a comma or a semi-colon should go. It’s time to change that.

Funny Mistakes

One of the most common punctuation mistakes is to form the plural with an apostrophe. This is sometimes called the “grocer’s apostrophe,” since it seems to happen all too frequently in supermarkets:

Would you have spotted that this should read “bananas”? It’s good to avoid such basic errors, but if we want to improve more substantially, we really need to study grammar.

Sentence Structure

The key to learning punctuation is to understand how the parts of a sentence work together. Take the following sentence:

If you’ve watched enough TV detective series, then you’ll get the impression that the most dangerous places in the world are Oxford, small islands in the Caribbean, and pretty much anywhere in the British countryside.

Why the commas? The first one is to separate the dependent clause (starting with “if”) from the independent clause (starting with “then”). The remaining commas separate the items in a list. People often argue about whether the last one is necessary, given that we’ve already used “and.” The added comma is known as the Oxford comma: it is increasingly preferred, as it provides more clarity.

The point, however, is that knowing something about sentence structure makes punctuation much easier.

The Breathing Theory of Punctuation

What you want to avoid, by contrast, is adding punctuation marks such as commas and semi-colons whenever it sounds like there is a pause. Writing is not like swimming, where you take regular breaths between strokes. It’s quite possible to have an entire sentence without punctuation, other than the initial capital and the final period. Although our pauses and our punctuation marks will often line up, the breathing theory of punctuation is imprecise and best avoided.


There is a real beauty to punctuation. Once you see how the different parts of a sentence work together, you’ll feel more at ease, even with some of the trickier punctuation marks. You might even take pride in being able to use a semi-colon or a dash effectively.