Semi-colons: How Hard Can They Be?

Semi-colons are one of the most commonly misused punctuation marks around and most of us probably know someone who is adamant they know exactly how to use them. Spoiler alert: they're wrong!

So, what is a semi-colon?

This is a semi-colon (semicolon for the hyphen haters among you): a punctuation mark made up of a comma on the bottom and a full stop (period) on top.

There are four main uses for a semi-colon: to separate two closely-related main clauses, to imply a stronger separation in a sentence already divided by commas, to replace a full stop when a capital letter/symbol starts the next sentence, and to separate list items containing commas.

Linking clauses

A semi-colon can be used as a sort of middle ground between a comma and a full stop, indicating that the clauses (which must be able to stand on their own as grammatically complete sentences) are closely related and either compliment or parallel each other.

An example of this could be:

The cat jumped on the chair; the chair fell to the floor.

Here a comma would imply too close a relationship without a conjunction (try the following sentence with different connectives: and, but, therefore):

The cat jumped on the chair, [conjunction] the chair fell to the floor.

The cat jumped on the chair, but the chair fell to the floor.

The cat jumped on the chair, therefore the chair fell to the floor.

The cat jumped on the chair, and the chair fell to the floor.

and a full stop would imply that both clauses are independent:

The cat jumped on the chair. The chair fell to the floor.

With a semi-colon it is implied that the cat jumping on the chair made the chair fall over.

The cat jumped on the chair; the chair fell to the floor.

Replacing a comma

If you have a sentence already subdivided by commas, a semi-colon can be a useful tool to denote a larger division.

He stepped onto the road, which was empty save for a pair of parked cars, and saw her standing by the tree; but instead of calling out her name, he simply waved until she noticed him.

Written with only commas, this text can feel messy or confusing to a reader.

He stepped onto the road, which was empty save for a pair of parked cars, and saw her standing by the tree, but instead of calling out her name, he simply waved until she noticed him.

And with a full stop the separation is too large (and the second sentence begins with “but” – something most people try to avoid!).

He stepped onto the road, which was empty save for a pair of parked cars, and saw her standing by the tree. But instead of calling out her name, he simply waved until she noticed him.

Using a semi-colon here helps to aid clarity and readability while keeping the passage as a single sentence. It implies a stronger separation than a comma while maintaining the connection a full stop removes.

Replacing a full stop

Being the half-way point between a comma and a full stop, a semi-colon can also be used to simply replace a full stop (not all full stops, though!).

For this experiment, participant 𝑥 and participant 𝑦 are in a room; 𝑥 will yawn, if 𝑦 yawns too then we know yawns may be contagious.

Written with a full stop, the text looks like this.

For this experiment, participant 𝑥 and participant 𝑦 are in a room. 𝑥 will yawn, if 𝑦 yawns too then we know yawns may be contagious.

Here the second sentence starts with a lower case symbol, which can be both unattractive and confusing to readers (is it meant to be lower case and a comma or upper case and a full stop? Is it a mistake?).

This use of a semi-colon is more commonly seen in scientific or mathematical writing, but can also appear in other forms of fiction and non-fiction writing (especially in hard science fiction, such as Cixin Liu’s Remebrance of Earth’s Past series).

Separating a list

The final way in which a semi-colon can be used is in a list where commas appear in the listed items. An example of this could be when mentioning people with their titles:

On the panel of experts are John, a professor of robotics from Swansea University; Jenny, an astrophysics researcher at Oxford University; Ben, the head of psychology at Cardiff University; and Chris, an expert of philosophy at Exeter University.

Written only with commas, the passage is much less clear and its meaning more ambiguous:

On the panel of experts are John, a professor of robotics from Swansea University, Jenny, an astrophysics researcher at Oxford University, Ben, the head of psychology at Cardiff University, and Chris, an expert of philosophy at Exeter University.

When only commas are used in the list, you could be forgiven for thinking there are four named experts and three experts mentioned only by title on the panel; when written with semi-colons it is clear there are four experts named with their titles on the panel.

Common Misunderstandings

There are a few misunderstandings when it comes to semi-colons that I’ll dispel here.

“The only punctuation that can follow a semi-colon is a full stop.” – For a while this was taught to students, but it is poor advice. After all, if it were true, a semi-colon could never be used in a list!

“Semi-colons go before lists.” – A common mistake but untrue. A semi-colon can be used in a list (see above) but colons (:) are used to start lists.

“You cannot use a semi-colon before a connective (but, and, however).” – In many cases it is preferable to use a semi-colon over the alternatives. This rule is too prescriptive to be helpful – always be wary of prescriptive “there’s only one way” advice.

“Writing aids like Grammarly say my semi-colon use is perfect, so I don’t need to know any more.” – Semi-colons are to writing aids what duct tape is to a DIY-er: rarely the best tool for the job but great for a quick, easy fix that ‘technically’ works. Because of their versatility, semi-colons are rarely incorrect on an technical level, but be wary of overusing them. Too many and your prose will suffer: just as a shelf could be held up with duct tape, the queston is whether it should. We all know that shelf would be stronger if we’d used the right tools for the job.

Of course, some people just choose to omit semi-colons altogether, and that’s completely fine! After all, it’s your story and your way of writing it; but knowing how to use them correctly can help you craft stronger prose and make your writing more engaging and easier to read.

So, do you like using semi-colons? Now you know how they can be used, will you use them more? Get in touch and let me know!

And if you would like a second set of eyes to check check no semi-colons have taken the place of an honest colon, get in touch.

Last updated: March 6th 2025.