A possessive apostrophe shows that something belongs to someone.
Where you put an apostrophe depends on whether you are talking about a singular noun or a plural noun.
Singular nouns -- means there is only one of them.
e.g. tree, woman, car, Mandy, Billy, dog
The tree's branches waved in the wind. (The branches belong to the tree.)
You add an apostrophe and an 's' to your noun.
If your singular noun ends in an 's' already, just add an apostrophe at the end. ----> Thomas' book. (The book belongs to Thomas)
Plural nouns -- means there is more than one thing.
e.g. trees, girls, boys, cars, dogs, tables, women
(These usually have an s on the end.)
The trees' branches waved in the wind. (The branches belong to several trees.)
The apostrophe goes after the end of your plural noun. trees --> trees'
If your plural doesn't end in an 's' , add an apostrophe and then an 's'. women --> women's
For more information, see the BBC Bitesize website!