I know a few people would like a proper introduction to commas and how to use them, so I’ve compiled a guide here based in part on the chapter on commas in Advanced Writing Skills for Students of English. Some of the specific areas I’ve gone into more detail on in the past, so there are some links to additional reading too.
The main thing I’d say you need to understand about commas is that they separate different parts of a sentence. Their chief function is to make sentences clearer by grouping words, phrases and clauses. With that in mind, mastering commas is not really about learning rules or patterns specific to commas themselves, as their use can be flexible depending on the needs of the sentence. To use commas effectively, what you really need to know is how to break up a sentence.
How do commas work?
A comma finds its place, essentially, when we have an opportunity for confusion. When it might not be clear where one sentence part ends and another begins, that is where a comma helps. This can include instances where you have multiple verbs and want to be clear how the actions are separated, or how they relate. It can also help when you have lists, to make it clear where one phrase ends and another begins. You might also need commas to help separate unexpected information, such as where an adverbial or aside appears out of its typical order, which could confuse the way the sentence is read.
With that in mind, I’d actually suggest starting by learning about the parts of speech and typical sentence structure – most of which is covered in my guide to word order here. For a very quick introduction, though, the main structural areas comma help with are in clarifying noun phrases (the subjects and objects of our sentences), clauses (where we separate complete actions) and phrases containing information that appear in unexpected places.
When you understand sentence components, you can clearly see where exactly the comma should appear, around the grouped sentence components and not randomly within them. You can then effectively answer a simple question to decide if a comma is necessary or not: is it easier to read/understand the sentence with or without a comma?
The option less likely to confuse or interrupt your reader is best, which is true of most writing rules.
Going into more detail, we can look at some specific conventions which I’ve already covered on the blog. Here’s a summary of some additional reading there:
Commas and Clauses
- Using Commas to Separate Clauses: this article goes into detail about how we break up longer sentences, where you have more than one main verb. The presence, or absence, of a comma can change the way we understand the clauses’ interaction (typically signally a defining or non-defining relationship) or can alter the pace of the sentence.
- Understanding Comma Splices: this article goes into detail about what happens when commas are used inappropriately to connect clauses that do not connect clearly.
Commas and Clarifying Information
- Commas, Lists and the Serial Comma: this article explains how we use commas to help separate groups of more than two items, and how the serial/Oxford comma works.
- Using commas to add information: this article covers the other application of breaking up information, where we put sentence components in unexpected places.
The little bit I’m missing on the site at the moment is about how we use commas with adverbials, which I’ll try and add soon.
That’s all for now, let me know if you have any questions, and if you’d like more tips on sentence structure or writing skills, do check out all of my books.
