Possessive Apostrophes
This apostrophe tells you who owns what.
It indicates that someone owns something.
There is a trick to remembering how this is done - think of the tail of the apostrophe as pointing to whoever has ownership.
So:
The kite of the boy. = The boy's kite.
The kite of the boys. = The boys' kite.
Let's look at that again ... slowly.
The bone of the dog, would be - The dog's bone.
The bone of the vicious herd of wild killer-dogs, would be - The dogs' bone.
See that? Notice how the tail of the 'postrophe is pointing to the number of dogs? Very good.