Semi-Colons

The semi-colon has two uses, and one of them is very easy to remember:

the semi-colon separates long items in a list

I came home from work; brushed my teeth; took off my clothes; and then ate my dinner.

Aside from this simple use, however, the semi-colon is the punctuation mark that causes the greatest difficulty. Put simply:

the semi-colon is a substitute for a full stop.

But of course it is not as simple as that. The semi-colon seems to be inherently confusing, and because of that this handout is going to explain it from the basics on up. I’ll start with some grammatical facts that are important to understanding when to use the semi-colon, then move on to explaining the semi-colon in light of these facts. This should make grasping it much easier.

Clauses: A Guide

A clause is a collection of words that make up a sentence or part of a sentence. Grammar recognizes two basic types of clauses: MAIN clauses (which are also called INDEPENDENT CLAUSES) and SUBORDINATE CLAUSES (which are also called DEPENDENT CLAUSES)

A MAIN/INDEPENDENT clause can stand on its own.

A SUBORDINATE/DEPENDENT clause cannot stand on its own (it depends on another clause).

I (Main Clause) went to the store, but (Subordinate Clause) I forgot my money.

Because:

I went to the store can stand on its own

but I forgot my money cannot stand on its own

Sentences: A Guide

A sentence is a clause that can stand on its own – in other words, a sentence is a main clause.

In order to qualify as a sentence, a clause must have two things: a VERB and a SUBJECT.

A verb is a doing word.

A subject is the thing that is doing the doing word.

For example:

I eat.
Edgar sneezed.

In some cases, the subject of a sentence is understood. This means it is not present, but we understand that it is there. Sentences where the subject is understood are usually commands:

[You] Sit!
[You] Shut up!

Once a clause has a verb and a subject doing the verb, it could be a complete sentence. This means you could put a full stop right there.

I eat.

Sometimes, however, a thing can qualify as a complete sentence without being a complete thought. This means you have to wait and put your full stop at the end of the complete thought.

For example, “Edgar bought” has a verb and a subject doing the verb, so according to the rules it’s a sentence. But in order to be a complete unit of thought (and to make sense!) it needs more, so you can’t put a full stop at the end and move on. Instead, you need to look for the end of the unit of thought. One full unit of thought = a full stop.

Two full units of thought? A full stop at the end of each unit of thought.

“Edgar bought a new raincoat” is a complete sentence and a complete unit of thought, and you put your full stop at the end of the unit of thought.

Edgar bought a new raincoat(.)

“Edgar bought a new raincoat it was too big for him” is two complete units of thought, so each needs to end with a full stop.

Edgar bought a new raincoat(.) It was too big for him(.)

Okay, now we have our ducks in a row; we know everything we need to know in order to understand semi-colon usage. So…

NOW WE COME TO THE SEMI-COLON

A semi-colon is essentially a substitute for a full stop. But unlike a full stop, a semi-colon does not stop a sentence. Instead, a semi-colon is a kind of hinge: it connects two parts of a sentence.

Now, because a semi-colon is “a substitute for a full stop,” you know it can only come at end of a full unit of thought. But a semi-colon also needs to have a full unit of sense after it.*

You wouldn’t write
I dressed in my favourite shirt. But no one else liked it.

Because

But no one else liked it

can’t stand on its own.

Therefore, you can’t write
I dressed in my favourite shirt; but no one else liked it.

What you can write, though, is:
I dressed in my favourite shirt; no one else liked it.

Because you would write:
I dressed in my favourite shirt. No one else liked it.

*this is because the second part of the sentence will end in a full stop, so it needs to be a sentence, too (but you don’t need to remember that).

You may have realized by this time, however, that there is another punctuation mark that is a kind of hinge: the comma. A comma also separates two parts of a sentence.

And this is the single most-common mistake writers make: they use the comma where they should use the semi-colon. This is called…

A COMMA SPLICE

Here is where the confusion starts:
A comma and a semi-colon are both hinges.

That is true. But:
A comma separates two UNLIKE clauses.

A semi-colon separates two ALIKE clauses.

The likeness or unlikeness does not have to do with meaning. Grammar is a cruel mistress: she does not care about meaning. Grammar cares about the grammatical units (noun, verb, subject, object) that make up a sentence. In this case, you need to determine if each clause has the same units of meaning.

If you have trouble with like/unlike, another way to understand the concept is:

A semi-colon separates two clauses that can each stand on their own.

A comma separates two clauses, at least one of which cannot stand on its own.

For example:

I dressed in my favourite shirt but no one else liked it.

I dressed (this can stand alone) in my favourite shirt but no one else liked it.

I dressed in my favourite shirt but no one (this cannot stand alone) else liked it.

Here you have two clauses that have different grammatical elements (each has a subject and a verb, but one also has a conjunction, “but,” a joining word) – they are unlike. Also, one of these clauses can stand alone, and one cannot. If you look up to the guidelines (↑), you will see that these two clauses should be separated by a comma.

But what do I do if my sentence has more than two clauses????

Good question! Sometimes you get a sentence like this:

I dressed in my favourite shirt which was blue no one else liked it.

In these cases, go through the clauses one at a time.

I (this can stand alone) dressed in my favourite shirt which (this can’t) was blue no (this can) one else liked it.

You already know that a main clause (can stand alone) and a subordinate clause (can’t stand alone) should be separated by a comma (because they are UNLIKE). So put in that comma:

I dressed in my favourite shirt, which was blue no one else liked it.

Now you need to remember something: as soon as you put a comma between two clauses, those two clauses are attached: they become two parts of one complete thought. This is actually quite clear in this case if you put some spaces between units:

I (one complete thought) dressed in my favourite shirt, which was blue no (another complete thought) one else liked it.

It might be useful to think of it this way:

Although you are punctuating the sentence forwards, that punctuation depends on looking at it backwards.

Because in order to determine whether you need a semi-colon or a comma, you have to see whether the clauses before make a complete thought (P.S. If they do, you need a semi-colon).

Now the only question remaining is

HOW IS A SEMI-COLON DIFFERENT FROM A FULL STOP?

Good question! And I want to start my answer by saying that if this answer doesn’t make sense to you, you never have to use a semi-colon at all. Just put a full stop after every main clause and before every main clause (or before its introductory word).

However, the answer is, whereas a full stop separates two main clauses, a semi-colon separates two main clauses that are so closely related that, if they had a conjunction between them, they could be joined in a single sentence – but are separate enough that it doesn’t feel right when they’re separated by a conjunction.

For example:

Oscar was wrong he began to titter in embarrassment.

Because each of these clauses has a subject and a verb, each could be a sentence, like this:

Oscar was wrong. He began to titter in embarrassment.

But that sounds too jerky. At the same time, though, if you tried to join them up using a

conjunction, that sounds wrong, too.

Oscar was wrong, and he began to titter in embarrassment.

So you use a semi-colon, because it connects them more than a full stop, but less than a comma and conjunction.

And there you have it: the semi-colon explained. Phew!

Practical Solutions:

Remember that grammar only cares about the grammatical elements in a sentence, not the meaning of the sentence.

Does your sentence consist of two main clauses with no conjunction between them? Use a semi-colon.

Does your sentence consist of a main clause and a subordinate clause? Use a comma.

Are the two clauses ALIKE? Use a semi-colon.

Are the two clauses UNLIKE each other? Use a comma

Be Aware of These:

Semi-colons take time to get used to. In the beginning, you may have to check the elements of a sentence, remember the rule, see if it fits the rule, and only then use or not use a semi-colon. Don’t worry; you’ll speed up with practice.

You will gladden the heart of every supervisor you meet if you learn the rules of correct comma and semi-colon usage.