Skip to main content

Academic writing

Expert guidance from Study Advice at the University of Reading

Knowing how to use punctuation properly is not just a matter of fussiness or pedantry. Appropriate punctuation acts like a set of 'road signs' to guide the reader through the ideas expressed in your sentences. Punctuation marks can tell the reader when to slow down, speed up and stop. By breaking up your sentences, they contain and structure your ideas.

This guide includes advice on using some of the most common types of punctuation. If you would like more detailed advice, or if English is not your first language, there are links below to other websites which include more detailed advice and interactive exercises. If you are a University of Reading student and English is not your first language, the Academic English Programme (AEP) provides training courses in academic writing skills, speaking skills, and pronunciation practice.

Punctuation in brief

  1. Use a comma to create a pause, to separate ideas in that sentence.
  2. Use a semi-colon to create a break, but recognises connection of ideas
  3. Use a colon to connect two sentences thematically
  4. Use a full stop to create the end of that sentence.
  5. Use an apostrophe to indicate ownership or missing letters/numbers.

Using commas

Commas are used to break up different parts of a sentence. They allow someone to make sense of what they are reading. Commas occur where ideas are grouped, to make it easier to understand these ideas. It may be helpful to think of commas as places where a reader might draw breath. The comma forms a natural place in a sentence where the reader can pause, to make sense of an idea. As a comma signifies a pause, it follows natural speech pattern. Here are some of the ways it can be used.

To separate words in a list:

He lost his house, his heritage, his hair, and his handkerchief.

To separate parts of a sentence:

Firstly, I would like to consider the merits of supplementing the diet with zinc extract. Secondly, vitamin C can be introduced to combat infection.

Here the comma separates the first word from the body of the sentence, to indicate that this idea is only the first.

To separate two parts of a linked idea:

After the French Revolution had taken place, many other European countries were concerned about civil unrest.
Many scientists believe in evolution, although some are trying to disprove Darwin's Theory of Evolution.

To separate a final phrase, which is an afterthought:

Few people enjoy arduous and demanding exams, especially on Saturdays.
I would like to run the London Marathon, if I were fit.

Using the semi-colon

The semi-colon contains a comma and a full stop. It may be helpful to think of semi-colons as halfway between the two. They are used in the following ways:

To link sentences that are closely related:

The night sky was the deepest sapphire; Claire realised that she had not observed its beauty until now.

A full stop between the two sentences would detract from Claire's observation, and a comma would not make enough of a break to allow the reader to make sense of the two ideas.

To link sentences that are in opposition to each other:

His research methods were fundamentally flawed; nonetheless, he collected the data.

In each of the examples above, the set of words after the semi-colon must be able to stand as a sentence on its own. However, there is a very common use of the semi-colon where this is not the case:

To separate items in a list:

Mrs Brown was assisted by other members of staff: Dr Benham from Animal Husbandry; Mr Gleeson from Botany; and Dr Chalk from Soil Science.

Using the colon

When a colon is used in a sentence, the parts it separates do not need to be complete sentences in their own right. Colons are used in the following ways:

To introduce a list:

The results of the indoor team games were as follows: Wessex came first, Bridges and Wantage were joint second, and Sibly came last.

To link two sentences thematically:

Psychological studies into domestic violence are usually centred on an idea of the nuclear family: Henry Davis decided that he should undertake a more radical approach to research in this area.

Here the two sentences could exist separately, but by connecting them with a colon the reader is led from one idea to the next.

To draw out a conclusion:

Language acquisition is a difficult but immensely rewarding task: without it, there is little hope for global communication.

Here, what is said in the first sentence is contextualised by what is said in the second sentence.

Using apostrophes

The apostrophe has two functions:

  1. To show that letters are missing. This is known as contraction.
  2. To indicate ownership. This is known as possession.


When letters are missing in a word, and the word becomes shorter, the apostrophe is used to show where the missing letters belonged.

For example:

  • I am becomes I'm
  • You will becomes you'll
  • They would becomes they'd

Contractions are used in informal writing. Essays and reports should not contain informal writing.


Apostrophes are also used to show that something belongs to something else.

For example:

  • The girl's hat - means that the hat is owned by the girl.
  • The girl's hats - means that the girl owns more than one hat.
  • The girls' hat - means that the girls all share ownership of one hat.
  • The girls' hats - means that the girls own several hats (or one each).

As you can see, the apostrophe usually comes before the 's' if the subject is single ('the girl'), and after the 's' if it is plural ('the girls'). However it may be different if the word for a single subject ends with 's' like princess, Venus or Socrates. One useful way to deal with this is to see if the 's' is pronounced.

For example:

  • Venus's arms or the princess's coronet

In both of these examples the 's' is pronounced, so there is an additional 's' with the apostrophe before.

  • Socrates' wife

In this example the 's' is not pronounced, so there is no additional 's' and the apostrophe goes after the final 's' in Socrates.


The cat licked its paws.

There is no need for an apostrophe, because 'its' is a pronoun in its own right which stands in for 'the cat's' and indicates ownership.

It's an amazing idea.

A missing letter has been replaced by the apostrophe, so it really means 'it is':


Whose shoes are they?

Here whose is a special kind of pronoun (like its) which indicates ownership already, so there is no apostrophe.

Who's coming to dinner?

A missing letter has been replaced by the apostrophe, so it really means, 'who is'.


The 1960s were a period of radical changes in morality.

In the '60s, public morality underwent radical changes.

1960s' morality was quite different to that which had gone before.

- In the first sentence, '1960s' is a plural referring to all the years between 1960 and 1969, so there is no apostrophe.

- In the second sentence there is a contraction with '19' missed off. The apostrophe replaces the missing numbers.

- In the third sentence, what is being referred to is the morality of the 1960s, so the apostrophe indicates possession.  

It is worth remembering that words may end with 's' because they are plurals, and not because they indicate ownership or contraction. Look at what the word is doing and apply an apostrophe only if appropriate.