How to use punctuation marks

Punctuation is a subject that many people find difficult but is very important for a writer to understand, master and apply correctly. Not all of the sections here relate to punctuation marks specifically, but the subjects are related.

Full stops / Periods

Full stops, also known as ‘periods’ in American English, are used to mark the end of a sentence. An additional use is to highlight an abbreviation when expressed in lower case.

punctuation marks
punctuation marks

Abbreviations expressed in upper case should not normally use full stops.

For example:

  • e.g. or i.e. or Apr. (for April)
  • CNN, RSVP, etc.


Commas are used to indicate that a pause is required in the sentence. The pause indicated by a comma is only slight, with longer, more significant pauses indicated by colons and semi-colons.

Commas can also be used to separate items in a simple list within a sentence, for example.

  • my favourite authors are Hiaasen, Brookmyre, Rankin and Forsyth.

They can also be used to provide a form of parenthesis, similar to the use of brackets, to include additional, but not essential, information. In this application, like the use of bracketed parenthesis, the sentence should still make sense if the phrases between the commas are removed. The previous two sentences here are examples of this usage.

Semi-colons and Colons

Semi-colons and colons, like commas, can be used to indicate the need for a pause in the sentence. They can also be used to indicate that additional related information is to follow the preceding part of the sentence. In general, the two parts of the longer sentence could be stated as sentences in their own right.

It is never necessary to use either a semi-colon or a colon although you may choose to use them to make your sentences more readable.


The apostrophe must be one of the most misused punctuation marks in the English language. They have only two specific uses: to imply possession or to denote missing letters. Apostrophes should not be used when making words plural.

For example, the following uses denote missing letters.

  • Don’t (as opposed to ‘do not’)
  • You’re (as opposed to ‘you are’)
  • I’m (as opposed to ‘I am’)

The following uses denote possession for singular nouns.

  • The child’s toy…
  • A writer’s inspiration…
  • My wife’s mobile phone…

Where a noun is plural and ends in ‘s’, the apostrophe should come at the end of the word, without the addition of another ‘s’.

For example:

  • Your parents’ house…
  • The students’ common room

However, if the noun is plural and does not end in ‘s’, then the apostrophe should be placed at the end of the word and an ‘s’ added after it. For example:

Where a noun is singular and ends in ‘s’, an apostrophe and a further ‘s’ should be used.


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