A Word about Apostrophes

This was written by Peta Jellis (OU T171 Tutor)

The apostrophe (‘) is used on two occasions:

1.         To show that letters are missing and two words have been combined.

2.         To show possessiveness, ie that something “belongs” to a person or “thing”.

1.            MISSING LETTERS

Good examples of this are don’t (meaning do not) and we’ll (meaning we will). 

The confusion usually starts with “it’s”.  But the same rules still apply.  The ONLY time you use “it’s” is when you actually mean it is.

2.            POSSESSIVENESS

The second time you use an apostrophe is to show possessiveness and clarity.  For example.

The horses saddle needed mending.

To decide whether or not an apostrophe is needed at all and where to put it, there are a couple of “tricks” I use.

Firstly, is turn the sentence around mentally to:

The saddle of the horse needed mending.

If I can make such a statement, then I know that an apostrophe is needed.

My next question is: How many horses am I talking about? 

If I have one horse, then the apostrophe comes BEFORE the s. e.g.

            The horse’s saddle needed mending

If I have more than one horse (who happen to be using the same saddle), then the apostrophe would come AFTER the s, eg 

The horses’ saddle needed mending.

Staying with the above example, if I had more than one horse each of whom had their own saddle, my sentence would be

The horses’ saddles needed mending.

Note that saddles have now become plural but there is no apostrophe required – it is a straight-forward plural.

The final confusion comes with sentences like:

The cat licked its tail.

The word “its” in this case is a possessive adjective, but the same rules apply as given in point 1 above.  NO APOSTROPHE needed – because if we put one in we would in actually be saying “The cat licked it is tail” which just doesn’t make any sense at all!

So, if I give the following examples:

1.         The tutor returned the student’s assignment.   

How many students?  How many assignments?

2.         The tutor returned the students’ assignments.             

How many students?  How many assignments?

3.         The tutor returned the student’s assignments.

                        How many students?  How many assignments?


1.         1 student, 1 assignment

2.         2 or more students, 2 or more assignments

3.         1 student, 2 or more assignments.

This covers the majority (but not all) occasions on the use of the apostrophe.  There are, as always with the English language, anomalies.  One which springs to mind is:

            Five years’ imprisonment

Again, this can be twisted around to “imprisonment of five years” so it is clear that an apostrophe is needed.  If we were talking about one year’s imprisonment, then it is easy to see where the apostrophe goes.  The general rule is that if the word which requires an apostrophe ends in an s, then the apostrophe comes AFTER the s.  Another example is Achilles’ heel where it would not make any sense to break a “proper noun” to put the apostrophe before the s in Achilles.