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!

If you found this article, useful, check out my book, Advanced Writing Skills for Students of English, for more advice on writing and editing.