Whilst some believe that the oxford comma adds clarity to sentence meaning, others believe that the meaning of a sentence is often clear enough without its presence. Also known as the serial comma, it is the final comma placed before the connecting words ‘and’ or ‘or’ in a list of three or more things.

Despite these persistent grammatical debates on its value and usefulness, there is a particular case to be made for using the oxford comma in scientific writing.  

In this article, we’ll discuss journal style variation regarding the oxford comma and provide practical examples and advice concerning when (and why) to use the oxford comma in scientific writing.

What is the oxford comma? 

The oxford comma takes its name from the Oxford University Press, where its usage has been recommended in the Oxford Style Manual for over a hundred years. Guidance reccomends that a final comma be used in a list of three or more items, before the ‘and’ or ‘or.’

For example: 

• The reagents were water, ethanol, and acetone. 

In the above example, the case can be made that the meaning of the sentence would be clear without the final comma between ‘ethanol’ and ‘acetone’. So, what is the consensus on the usage of the oxford comma in scientific writing?

Journal style variation 

The general ambiguity surrounding the necessity of the oxford comma has led to different guideline stances on its usage within journal publishing. 

For example, scientific journals following Chicago Manual of Style or APA Style guidelines generally require the consistent use of the oxford comma. However, to complicate things, some scientific journals do not explicitly state a preference for usage. Rather, they tend to demonstrate an implicit preference for usage or non-usage of the oxford comma.  

What most scientific journals do tend to agree on, however, is that an oxford comma should be used if it reduces ambiguity. And if it is used, usage should be consistent throughout the manuscript.

When (and why) the oxford comma should be used 

Omitting or including the oxford comma either changes meaning or is simply stylistic. In the former case, especially in scientific writing, where accuracy is paramount to research reproducibility and integrity, it is key that authors understand when an oxford comma should be used to clarify meaning.

For complex or multi-component lists 

Lists containing more than one component are commonplace in scientific writing. Such lists may detail chemical compounds, organism names, and procedural steps. 

Multi-component lists can provide a lot of information. Sometimes, the meaning of this information can be unclear if oxford commas are not utilised for clarity. Take a look at the following example:  

• The protocol requires washing and drying the membranes, blocking and probing with antibody and imaging and quantifying the bands. 

Because of the three compound items in quick succession, confusion is introduced without an oxford comma. Here it is again, but with the added clarity of the final comma, making each procedural step distinct.  

• The protocol requires washing and drying the membranes, blocking and probing with antibody, and imaging and quantifying the bands.

When there is a risk of items looking like an appositive 

Sometimes, the last two items in a list can function like nouns or noun phrases that explain the item preceding it. These nouns or noun phrases are known as an appositive. For example: 

• Samples were collected by the field researchers, Dr. Okafor and Dr. Lenz. 

In this case, the lack of an oxford comma before the connecting word ‘and’ creates the impression that Dr. Okafor and Dr. Lenz are the field researchers of the preceding item. However, this is misleading; the three listed parties are distinct. Using an oxford comma clarifies the meaning: 

• Samples were collected by the field researchers, Dr. Okafor, and Dr. Lenz.

Practical advice to remember 

These instances listed above are by no means exhaustive. There may be other unique examples that require the use of an oxford comma to clarify meaning. On the other hand, there may be instances where using it might have an opposite effect, making the meaning of the sentence more unclear.  

To ensure that clarity is always retained and meaning communicated effectively, authors must use the oxford comma as a reliable marker that clearly identifies when one item ends and another begins.  

As for consistency, MDPI recommends the use of oxford or serial commas. However, they may be omitted if done so consistently. It may be a good idea to default to the oxford comma unless the target journal explicitly prohibits it. Just remember to use it consistently throughout your scientific manuscript if you do so.