I’ve been mostly editing books lately, so a lot of my focus has been on little details of English in written work. A frequent topic for inconsistencies or complications is commas, hence I have produced a full group of articles about them on this site.

I was going to expand on some details about them again, but realised I have already covered most of the rules. Instead, I thought it might be useful to show some comma considerations in use, through an exercise. So today I’ve got a short exercise to help identify issues with commas in English.

What are the rules for commas?

There are lot of different ways that commas can be applied in English, which can be flexible or nuanced. The exercise below will test a variety of these. You can either study the rules first or have a go at the exercise and to learn from the answers. To revise the information I’ve shared before, have a look at these articles:

• How to Master Commas in Use (a summary of all the content)
• Using Commas with Adverbials
• Using Commas with Additional Information
• Using Commas to Separate Clauses
• Using Commas with Lists and the Serial Comma

Common Comma Rules and Mistakes Exercise

Consider the following ten sentences. Some include commas and some do not. Decide if each sentence is Acceptable, Requires Commas or is Incorrect. (Note I say Acceptable and not Correct because sometimes a comma may be optionable; they are not necessary right or wrong, but the question is if it works.)

1. The girl who served me coffee, was very nice.
2. Do you want ice cream, chocolate, biscuits, or cake?
3. However, it got here I want that stain cleaned off.
4. I want to go out but I don’t have any nice clothes.
5. He jumped on the train, as it passed under the bridge.
6. Jill travelled to Prague with Erin, her mother and her cousin.
7. I ran up the stairs too fast, and tripped on the top step.
8. She returned the food as there was a hair in it.
9. “Oh, no!” he cried in surprise.
10. If you want to go to the beach, don’t forget to bring a towel.

Answers

I’ve tried to explain my thinking in full below, to give a complete understanding of how I approach comma use. If you have any questions, or disagree, do feel free to comment below!

1. The girl who served me coffee, was very nice. – Incorrect; “who served me coffee” is either defining (no commas) or non-defining and needs an extra comma ( “, who served me coffee,”)
2. Do you want ice cream, chocolate, biscuits, or cake? – Acceptable; this is an example or a list with an Oxford/serial comma which is not strictly necessary but does not cause any confusion to include.
3. However, it got here I want that stain cleaned off. – Incorrect; the comma should come at the end of the complete adverbial phrase, “However it got here,” (and we can tell it is an adverbial phrase and not a separate clause because there is no conjunction).
4. I want to go out but I don’t have any nice clothes. – Acceptable; the sentence is short and easily understood, so a comma before “but” isn’t necessary.
5. He jumped on the train, as it passed under the bridge. – Incorrect; the comma separates the “as” clause as additional/incidental information, shifting the meaning to “because”, whereas without a comma the sentence flows together with “as” meaning the clauses occur at the same time.
6. Jill travelled to Prague with Erin, her mother and her cousin. – Incorrect; this may be unlikely to be misunderstood, but this is an example of where an Oxford/serial comma could avoid awkward confusion by clearly showing this is a list and not defining information (“Erin, her mother, and her cousin”). This doesn’t completely solve the problem, however, as we don’t know if the list is two or three people (reordering it so Erin is not first would solve this), but it is clearer with a comma than without!
7. I ran up the stairs too fast, and tripped on the top step. – Acceptable; this isn’t incorrect, as the comma can be used here to slow down the sentence or give the second clause the feeling of an after-thought/sequential action. However, without a particular reason for it, I would advise removing this comma as the sentence is short and flows better without a comma.
8. She returned the food as there was a hair in it. – Acceptable; a comma could separate the “as” clause as additional information, but is not required to clarify the sentence.
9. “Oh, no!” he cried in surprise. – Incorrect; this is a complete phrasal expression, which shouldn’t be separated by a comma, unless deliberately showing hesitation. (Consider the difference in response to a question: “Oh, no, that’s not what I meant.”)
10. If you want to go to the beach, don’t forget to bring a towel. – Acceptable; generally in conditional sentences when the “if” clause comes first, a comma between the clauses helps add clarity.

Reaching the end of my series on commas, here’s another brief extract from Advanced Writing Skills for Students of English to look at how commas are used with adverbial phrases.

This fits into my wider guide to commas that I’ve been adding to on the site; you can find the introduction and summary of other articles (with links) all here, in How to Master Commas in Use, so if you haven’t already read that I recommend starting there!

Otherwise, let’s begin… 

Using Commas with Adverbs and Adverbial Phrases

Commas often follow adverbs or adverbial phrases used at the start of a sentence. This is done in the same way as using a comma to separate a subordinate clause at the start of a sentence. These adverbials frame the sentence with information that would typically come later (such as time, manner, or a comment), placing information before the main clause:

• In time, we learnt the truth.
• Quick as a flash, she threw the flaming pan into the sink.
• Actually, there are no correct answers.

The comma comes directly after the adverb or complete adverbial phrase.

The adverb however is a well-known example of this, and is often taught as always being followed by a comma when placed at the start of a clause:

• However, the deal was not accepted.

This is only true when however is used to mean on the other hand / in contrast (as a linking adverb). But however may also be used to mean by whatever means, which does not use a comma. In the following example, however is part of an adverbial phrase, so the comma comes at the end of the phrase, not directly after the adverb:

• However much you want it, you cannot have my cake.

As always, let me know if you have any questions, and be sure to check out the other comma articles for more punctuation advice.

A problem many native English writers and foreign English learners have in common is combining independent clauses without the appropriate punctuation or conjunctions, often seen with what we call comma splices.

I thought this would be an interesting topic to cover, especially as I realised it’s not already in my Advanced Writing Skills book (and it’s a nice follow up to my recent look at serial commas!). So, I’m going to briefly explain what comma splices are, why (and how) they should be avoided and why they can sometimes be acceptable.

What is a Comma Splice?

Simply put, a comma splice is when you have a comma combining independent clauses, where you would otherwise expect to see a conjunction or conjunctive punctuation (for example a semi-colon, colon or dash), or two separate sentences. For example:

• She went into the basement. The lights weren’t working. = separate sentences
• She went into the basement but the lights weren’t working. = conjunction
• She went into the basement; the lights weren’t working. = conjunctive punctuation
• She went into the basement, the lights weren’t working. = comma splice

To break this down a little more, and help identify such splices, remember that an independent clause occurs whenever we have a new verb and subject, without any connectors that link it dependently to another clause (e.g. subordinating conjunctions like when, as, or relative pronouns like who, which).

In the example above, the verbs “went” and “weren’t” indicate distinct clauses, made clearer because we have separate subjects “she” and “the lights”. However, even if the verbs share a subject, which does not necessarily need to be repeated, a new active verb can still form a separate independent clause that needs connecting:

• She went into the basement and tried to turn on the light. = conjunction
• She went into the basement – tried to turn on the lights. = conjunctive punctuation
• She went into the basement, tried to turn on the lights. = comma splice

The second example here, with the dash, creates a sentence fragment, which can be more acceptably linked by a dash than a comma (though depending on the context even the dash might not be welcome; as always, the more formal a text, the more likely it would be to stick to expected rules and conventions).

Why do Comma Splices Matter?

In the examples above, the comma splices are technically incorrect. You might read them and think they make sense, though, so why does it matter? When compared to sentences that use semi-colons to bridge clauses, it might look like there’s little difference, after all.

Well, the simplest explanation is that commas are not intended to be used in this way and it’s therefore likely to cause confusion with readers. It can actively affect the way a sentence is read. How problematic this is depends on the sentence; the examples above aren’t confusing, but longer sentences or ones with different subjects could be. It can also make it more difficult to read as we won’t pause in the right places, creating a clumsy flow where information isn’t clearly separated:

• She went into the basement, the lights weren’t working, it was very dark.

By using a comma, we’d also miss the opportunity to demonstrate how separate ideas are connected. Without more context, for example, we could easily express different scenarios depending on the chosen connector:

• She went into the basement where the lights weren’t working.
• She went into the basement because the lights weren’t working.

But if you read enough in English, particularly in fiction, you’re almost guaranteed to come across some comma splices eventually. It’s an easy mistake to make, and an easy one to miss. It’s also sometimes done deliberately. This is most often the case where a writer wants to add information running directly on without distinct connectors. It’s less formal than using a semi-colon and more subtle than using a dash, both of which would be the more accepted styles. It can create a slightly different feel when we have a shared subject with a follow-on action that adds a response or feeling. Compare:

• She muttered under her breath; hated the dark.
• She muttered under her breath – hated the dark.
• She muttered under her breath, hated the dark.

In this example, it’s actually working similarly to an adverbial, but it gives it a particular twist: “hating the dark” would be the expected, grammatically correct form, but “hated the dark” sets the verb differently, as a rule, or a complete, emphatic action.

That said, it’s a technique that few writers can get away with. I read an Elmore Leonard book (Maximum Bob I believe) which was full of comma splices, for example, but Elmore Leonard was an exceptional writer with a very specific style (in this case often reflecting a character of a certain low class’s mode of language). It’s very much a case of only bending the rules when you have mastered them, and even then only if you can confidently justify why you’re doing it – and note that it is only justifiable in very specific circumstances, which will often fall into the realm of deliberate mistakes anyway.

How to Avoid Comma Splices

Once you’ve got the hang of identifying independent clauses, to avoid comma splices ask yourself if your clauses are appropriately connected. If you find they’re not, this is fairly simple to fix. Let’s go back to our original example:

• She went into the basement, the lights weren’t working.

Most simply, we could separate the clauses into separate sentences:

• She went into the basement. The lights weren’t working.

To demonstrate a particular relationship between clauses, or generate a particular flow, you could replace the comma with an appropriate conjunction:

• She went into the basement but the lights weren’t working.

To connect the clauses closely, speeding the text up and demonstrating a relationship without spelling it out, you could use a semi-colon:

• She went into the basement; the lights weren’t working.

This could also be done with a dash, though the choice here is a matter of style and (as with the splices themselves) dashes might not be universally accepted. Also note that conjunctive punctuation like this might bridge the clauses correctly, but it doesn’t necessarily make much sense as a choice if there isn’t a clear reason that they’re closely connected. In this example, for example, it would work better if we had an indicator of why the clauses are connected, such as an adverb:

• She went into the basement slowly; the lights weren’t working. (the second clause accounts for how she went, slowly)

I hope this helps as a bit of a crash course in comma splices; there’s certainly more nuance that we could go into them and the examples you find in the wild can lead to lots of questions. There’s also controversy connected to this. Purists will say comma splices are unacceptable at any time (and if you want to be safe that’s a reasonable view to follow), whilst others may use them consistently, and clearly, without even knowing how or why. It’s one of those areas of English that can cause arguments, but as with all these things, the trick is to understand how and why it happens, and from there you can decide for yourself how and why it matters.

Today I’m going to look at another specific use of commas in English, particularly how we use them in lists, and how the controversial serial comma or Oxford comma works.

This builds on a couple of articles about specific uses of commas that I’ve shared in the past: Using Commas to Separate Clauses and Using Commas to Add Additional Information. These are all notes taken from my more comprehensive Advanced Writing Skills Books, if you want more tips like these!

So, to get started: commas (,) are used in English to separate items in lists of three or more words. Lists of different kinds of words connected by commas can include lists of nouns, verbs, adjectives, and adverbs.

• We ate cheese, ham, and tomatoes. (nouns)
• On Saturday, Doris read, swam, and rested. (verbs)
• They bought a new, tall, glass door. (adjectives)
• Slowly, carefully, and deliberately, she opened the metal box. (adverbs)

What is the serial comma / Oxford comma?

Lists may or may not have a comma placed before the co-ordinating conjunction (and). This is called the serial comma, the Oxford comma or Harvard comma. Some English speakers argue that it is necessary while others believe it should be omitted. The truth lies somewhere in between:

• A Full English breakfast consists of eggs, beans, sausages, and bacon. (serial comma)
• A Full English breakfast consists of eggs, beans, sausages and bacon. (no serial comma)

In the above example, adding or removing the comma is unlikely to make any difference to how the sentence is understood. It can be argued, however, that in different contexts the comma may add or remove clarity. In the following sentences, the comma makes it clear how many items are in the list:

• We ate ham, tomatoes, and eggs. (Comma separates three different food types.)
• We ate ham, tomatoes and eggs. (No comma leaves the possibility that the three foods were combined.)
• Dedicated to my co-workers, Paul and Jim. (No comma suggests Paul and Jim are the co-workers.)
• Dedicated to my co-workers, Paul, and Jim. (Comma suggests Paul and Jim are thanked in addition to the co-workers.)

The serial comma can cause confusion, however, when it makes an item in a list appear to be additional information:

• The group included a doctor, Jim Smith, and a baker. (suggesting the doctor is called Jim Smith)
• The group included a doctor, Jim Smith and a baker. (suggesting Jim Smith is a third member of the group)

When should you use serial commas?

The particular cases for using the serial comma can depend entirely on the sentence: as these examples illustrate, it can sometimes remove ambiguity and can sometimes cause ambiguity. Generally, the serial comma is encouraged by the majority of American style guides and some British style guides. In-house guides or publications may either encourage or discourage it, so it is worth knowing what is acceptable for your particular piece of writing. However, this is a rare case where consistency is not always the best policy. The demands of a particular list may make the serial comma more or less useful.

In cases where the meaning appears to change with or without the comma, and neither is fully clear, it may be best to reword the sentence. In the examples below, neither option is clear:

• Mary travelled to New York with Jim Smith, a doctor and a scholar. (Is Jim Smith both a doctor and a scholar, or did Mary travel with three people?)
• Mary travelled to New York with Jim Smith, a doctor, and a scholar. (Is Jim Smith a doctor or did Mary travel with three people?)

Depending on which meaning is true, the list could be reworded, perhaps with a relative clause or an additional conjunction, or by re-ordering:

• Mary travelled to New York with Jim Smith and a doctor and a scholar.
• Mary travelled to New York with a scholar and Jim Smith, who was a doctor.
• Mary travelled to New York with a doctor, a scholar, and Jim Smith. (with or without the serial comma)

That’s all from me on commas for today! If you want some more uses, do check out the articles I listed above, Using Commas to Separate Clauses and Using Commas to Add Additional Information, and for detailed tips on writing check out Advanced Writing Skills!