The Ten Uses of a Comma

Ever wondered how to use a comma? No. Then you probably should, I t can help your writing and editing. Here the uses of commas in academic English are covered. The first five are the most important in terms of overall sentence structure, whilst the next five cover some other technical comma usage below the level of the clause.

If you are looking for an overarching rule then it is this: keep it simple. Learn to do the basics correctly and then develop sophistication when appropriate. The longer your sentences the more complex they will be, and correspondingly, the more sophisticated your use of commas, and other punctuation, will have to be to maintain clarity.

1. Linking coordinating main clauses

Commas are used to separate main clauses divided by one of the following coordinating conjunctions, such as but, and, or, for, nor, yet, so.

Example :

We were unable to locate the cause of pain, so the patient’s discomfort continued.

Example :

The data was collected easily, but conclusions proved difficult to reach.

Example :

Home owners continue to suffer instability in the housing market, and economists are unable to provide a satisfactory analysis of market volatility.

NOTE: some people will say that it is unnecessary to put a comma before a coordinating conjunction, particularly when both the main clauses are short. As such, both of the following are acceptable:

Example :

Prices rise and prices also fall.

Example :

Prices rise, and prices also fall.

However, a comma should not be used when a coordinating conjunction connects two or more verbs to the subject of the sentence. For example:

Example :

Jane Austen mastered her own art and developed possibilities for the future direction of the novel. (Correct)

Example :

Marx was financially indebted to Engels, and personally enriched by their friendship. (Incorrect)


2. Marking off introductory and contextualising words and phrases at the start of the sentence

Introductory and contextualising phrases are often used at the start of sentences in academic English. There are three main types: clauses giving information on the position of the main clause in time and space; clauses adding circumstantial or judgemental information; and introductory words and phrases that move the writing on and can indicate argumentative shifts. We will consider each in turn.

Example: Time

Prior to Bourdieu and Foucault, twentieth-century French philosophy was permeated heavily by Marxist and phenomenological thought.

Example: Space

Outside of the logical positivist paradigm, Hawthorn (1967) contemplated the possibilities of meaning when not subject to empirical verification.


Example: Circumstantial or judgemental

Although well constructed, the empirical studies involved have proved inconclusive.


Example: Argumentative shifts

However, we have not been able to illustrate a significant relationship between childhood obesity and increased marketing expenditure.


In the first example, the phrase ‘Prior to Bourdieu and Foucault’ gives the main clause greater temporal specification. The second example uses an introductory clause with a spatial preposition ‘outside’, marking the metaphorical limits of the subject of the main clause. In the third example, the introductory clause passes judgement, as an additional comment, on the studies carried out. While in the final example, ‘However’ functions to introduce the sentence and mark a shift in the writer’s assertions. All the introductory elements in the sentences above could be removed and the sentences would still make sense and maintain their core meaning. Including these introductory elements adds a degree of sophistication and detail.


3. Inserting additional information at the end of a sentence

This use of a comma marks off phrases in a similar way to the previous examples of introductory and contextual phrases at the start of the sentence. Without wanting to add to much technical detail, both these types of additional phrases add what grammarians and linguists would call adverbial and prepositional phrases. These phrases can often occur either at the beginning, end, or even the middle of a main clause. Their mobility and optional nature are the key ways in which you can identify them, which is useful if you are trying to unpack your writing when editing early drafts.


Early approaches to grammar were idealised and rule governed, rather than based on applied observations.

Note how in the previous example the additional element could just as easily be put at the front of the sentence and remain coherent. In this next example the additional information cannot be moved around the sentence (this is an example of 2.5), but both the example above and the one below are subordinate clauses unable to stand on their own.


Herrington (1999) argues in the context of his research into racism and the state, which contrasts state and community driven projects, that greater social inclusion is achieved by…


4. Signalling implications, examples and introducing argumentative points

Certain words, used along with a comma, are very important in academic writing when signalling implications, examples and introducing argumentative points. If a sentence starts with a linking phrase or word then a comma should be used. Examples of linking words and phrases are, however, moreover, nevertheless, for example, as such, consequently, furthermore, in fact, indeed and similarly, amongst others.


In summation, a negative impact was recorded.



Thirdly, the implication of their argument is unfounded.



Similarly, experimentation is a necessary process to scientific investigation.


5. Parenthetical elements mid-sentence

These are subordinate clauses marked which add addition information as an extra comment or aside.


Doctoral dissertations and other academic genres are undergoing a period of significant change, and this will certainly continue, due to a new research agenda and new technology.


6. Forms of address (appositives) and places names

These conventions are probably familiar to people but for comprehensiveness and accuracy of use are included below.

Example: Appositives

James Smith, Professor of Genetics, pioneered research in human genetics.


Example: Places

CaledonianUniversity, Glasgow, pioneered research in nursing.


7. One of a kind

Commas help distinguish when something is one of a kind and not one of many. For example:


Lilith frequently spoke of her late husband, Jeremiah, on these occasions.

If Lilith were a polygamist or her religion afforded her the opportunity to have several husbands or she was windowed more than once then the commas could be removed. For scholarly writing, one must be more careful when referring to things like publications. The next example would be incorrect:


Professor Smith published his seminal work in the UK based journal, Rheumatology, for maximum impact.

Rheumatology is not the only UK based journal. Therefore, the following would be better:



Professor Smith published his seminal work in the number one UK based journal, Rheumatology, for maximum impact.

There can be only one ‘number one’ journal, therefore, Rheumatology must be enclosed in commas.


8. Lists and multiple adjectives modifying a noun

Commas are used to separate components of a list.


This study selected males aged 20, 25, 30 and 35.

Commas are also used to separate coordinating adjectives which modify a noun but not non-coordinating adjectives. Coordinating adjectives are of equal status and the final adjective in the list is preceded by ‘and’. One can recognise coordinating adjectives if: their order can change without effecting meaning; and ‘and can be placed in between them without effecting meaning. For example,

Smith’s exciting, well researched and influential study was initially ignored.


The list in this sentence can be reordered without becoming grammatically incoherence,

Smith’s well researched, influential and exciting study was initially ignored.


Non-coordinating adjectives cannot fulfil the above conditions, as in,

Smith’s new rheumatology study is groundbreaking.


The order of these two adjectives cannot be reversed; ‘Smith’s rheumatology new study’ would just not make sense. The initial adjective ‘new’ is subordinate to the second adjective ‘rheumatology’. Therefore, in instances such as these commas are not used.


9. Setting off quotations

This is probably very familiar to scholarly writers. The two main uses are marking reported speech and introducing quotations.

Example: Quotations

Smith (1956) noted, ‘subjects presented with extremely large facial cysts on the third day of the trial’.


Example: Reported speech

“The facial cysts were particularly painful and smelt a lot”, reported one patient in Smith’s (1956) study.


 10. Numbers

Commas are used with large numbers over a thousand. For example,








Full stops, not commas, are used in decimals.

And that’s about it, but a note of caution. The above are presented as if they are ‘rules’; I prefer to view them as conventions. Just because you can use a comma doesn’t necessarily mean you have to. In the setting out of appositives and numbers the conventions are very strong and always aids clarity. However, in other instances commas can be useful in indicating the different types of clause relationships that exist in the sentence you have constructed, but if you put a comma everywhere it is possible to the sentence can look cluttered or even confusing. In these instances the question is, what aids the reader? This may be quite subjective but think about using commas to aid communicating the meaning you intend.