What we tell proofreading course learners about commas

Aside from apostrophes, commas have to be the trickiest bits of punctuation to understand. We cover this on our proofreading course

I mean, every time you put a comma in, your proofreading and editing tutor takes it out and puts a comma in another place. Or at least, that’s what my proofreading and editing course students tell me!

Or, you put too few in. Or, too many. And when you do a Google search for advice, you get bombarded with terms like clauses, phrases, conjunctions, introductory elements etc, when all you want to find out is where to put them so you can hand your web writing assignment in.

It’s all about making the sentence mean what it is supposed to mean

Yes, simple really.

So, start off with no commas in your sentence:

Additional locations have been identified such as railway stations bus stations outside busy malls local parks and recreational areas and they have decided to put special bins in these areas because there is so much litter there.

Then, ask the following questions:

First: Does it include a list of items?

Yes: railway stations bus stations and local parks and recreational areas.

So: place commas after each element in the list, but not before the last ‘and’ in the list:

Additional locations have been identified such as railway stations, bus stations, outside busy malls, local parks and recreational areas and they have decided to put special bins in these areas because there is so much litter there.

Why? To group together words and phrases so that you get the correct mental image of what they are talking about. If the above punctuated list is made into a bullet list, you get:

railway stations
bus stations
outside busy malls
local parks
recreation areas

If you didn’t have a comma after ‘bus stations’ it would look as if only the bus stations outside busy malls had been chosen.

Second: Does it include coordinating conjunctions?

These are words like and, so, but, nor, yet, or for, that join two complete clauses (a clause is a sentence that can stand on its own).

Yes it does:

This could have been written:

Additional locations have been identified such as railway stations, bus stations, outside busy malls, local parks and recreational areas. They have decided to put special bins in these areas.

This means that there are two clauses in the sentence, which have been joined with ‘and’, so you put a comma in to show that what comes next is a whole new thought.

What to do: put a comma before the underlined ‘and’:

Additional locations have been identified such as railway stations, bus stations, outside busy malls, local parks and recreational areas, and they have decided to put special bins in these areas because there is so much litter there.

Third: Is there the word ‘because’

Yes: because there is so much litter in those places.

What to do: You do not need to put a comma before ‘because’ unless it could mean the wrong thing without it. Our sentence doesn’t need it as it makes sense the way it is, but have a look at this:

She wasn’t hungry because her sister works in a café and she had watched her eat a huge sandwich.

It could mean:

that she wasn’t hungry because her sister works in a café OR
that she wasn’t hungry because she had eaten a sandwich (this is the right meaning)

So, you put a comma after ‘hungry’ to make sure people understand it:

She wasn’t hungry, because her sister works in a café and she had watched her eat a huge sandwich.

Fourth: Are there any introductory elements?

These are words or phrases that set the scene, such as:

However
Until he arrived
While they were waiting

There are none in our sentence, but this is how they work:

There are three main reasons for using commas after these elements:

to separate them from a main clause
to indicate a pause
to avoid confusion

Here is a main clause starting with ‘therefore’:

Therefore, it is important that you use commas in your writing.

You can see that what follows the comma can stand on its own, so it is separated by a comma. It also indicates a slight pause when you speak.

Here is an example of using a comma to avoid confusion:

Until the summer classes will be held in the hall.

Until the summer, classes will be held in the hall.

Fifth: Are there any parenthetical elements?

These are parts of the sentence that could be left out without changing the meaning of the sentence.

Here are two examples:

Vivienne, the most intelligent proofreader in the firm, was always late.
His wife, June, made the best pies.

What is between commas is not necessary to the meaning.

But, watch out for this:

His son Brett was good at rugby.

If you put commas in either side of ‘Brett’ it means that you can remove the name:

His son, Brett, was good at rugby.
His son was good at rugby.

Which is OK, but what if he has more than one son? This would be confusing, as people would assume that he has only one son and that he was good at rugby.

So, if more than one person can take the title, do not put commas in.

Sixth: Is there a quote?

If a quote is split in the middle of a sentence, you use commas to indicate that it is still a single sentence:

“That Rolls Royce there,” he boasted, “is mine.”

There are other reasons commas should be used, although these are the main ones. You can check them out here: http://www.grammarbook.com/punctuation/commas.asp

What not to use a comma for:

I see so many comma splices these days, but it seems that many people don’t even know what they are, let alone know that they are incorrectly punctuated sentences.

A comma splice is where two clauses have been joined with a comma but without a coordinating junction.

For example, here are two clauses: