Get your apostrophe right!

 The apostrophe has 2 functions:
1. Contractions
2. Possession

Contractions

The apostrophe is used to indicate the missing letter, eg:

• She's told him = She has told him
• I'm here = I am here
• I can't = I cannot
• I wouldn't = I would not

Beware :

• your = belonging to you; you're = you are
• its = belonging to it; it's = it is or it has (its' does not exist)
• there = over there; their = belonging to them; they're = they are

Possession

When the possessor is single (ie, just one person or thing), we indicate possession by using an apostrophe followed by the letter s:

• The man's coat
• My sister's hat
• The lady's dress

When the possessors are plural (ie, more than one person or thing), we indicate possession by placing an apostrophe after the final s:

• The girls' bicycles
• My cousins' parents
• The secretaries' desks

However:
when a word changes completely in the plural, the apostrophe remains before the s:

• The men's books
• The children's toys
• The women's bags.

Apostrophes are not required where there is no possession eg:

• The PAs visited the seminar.
• The PCs were working well.
• She was born in the 1960s.

If the subject is followed by a verb an apostrophe will probably not be needed, if it is followed by a noun then one may be required

 See also:

• Chris's car (1 Chris)
• Mr Bridges' car (1 Mr Bridges and we don't make the extra s sound)
• The prince's car (1 prince)
• The princes' car (2 or more princes but still 1 car)
• The princess's car (1 princess)
• The princesses' car (2 or more princesses but still 1 car)
• The Joneses live next door (no possession but more than 1 person called Jones)
• The Joneses' car (more than 1 person called Jones who share a car)