[ QUOTE ]
's is only used when you have an "is" after a word and want to shorten the sentence, from what I remember. "my friend's dad" would sound like "my friend is dad" and that can't be right. So, it has to be "my friends dad"
[/ QUOTE ]
Apostrophes are used to show possession.
[ QUOTE ]
Main Entry: apostrophe
Function: noun
Etymology: Middle French & Late Latin; Middle French, from Late Latin apostrophus, from Greek apostrophos, from apostrophos turned away, from apostrephein
: a mark ' used to indicate the omission of letters or figures,
the possessive case, or the plural of letters or figures
- apostrophic adjective
[/ QUOTE ]
I think you are referring to one of the most common misuses of the apostrophe. It is not supposed to be used with possessives of personal pronouns.
WRONG: The car is <font color="red">her's</font>, not <font color="red">their's</font>. <font color="red">It's</font> color is purple.
RIGHT: The car is <font color="green">hers</font>, not <font color="green">theirs</font>. <font color="green">Its</font> color is purple.
Remember the picture of the guy holding up the sign that read, "Somewhere in Texas a village is missing <font color="red">it's</font> idiot." Well, the joke was on him. And he didn't get it.
It is perfectly ok to use an apostrophe to indicate possession. The dog's hair. Bill's toolbox. The business's customers.
And actually now that I've looked it up, I was wrong on one of my examples. If you have a plural word that doesn't end with the letter "s", you just add -'s to the end to make it a possessive. The children's educations. The single appostrophe at the end is only for plural words that do in with the letter "s".
Mike
P.S. I plagarised a lot out of a handbook I was forced to buy for my first semester of rhetoric back in 1998. It's called
The Little, Brown Essential Handbook for Writers (second edition) by Jane E. Aaron. ISBN 0-321-03805-3. It's small and very easy to use. It has all of the grammatical uses and a lot of other useful stuff.