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What is the correct possessive for nouns ending in s?

First, sorry about my English.

I would love to know when I need to add 's at the ending of the word.

1) When I meant is, like...

He's famous.


he is famous.

2) When it's like possession (don't know is this right word for that) of that word? And... exactly when??

John's book.

Dream's city.

Alien's ship. (one alien)

Aliens's ship. (two or more aliens)

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marked as duplicate by Robusto, RegDwigнt May 1 '11 at 21:31

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

looks like you already know... – Matt E. Эллен May 1 '11 at 19:59
We have a ton of more specific questions around that address various parts of this question here. E.g. What is the correct possessive for nouns ending in s or What is the best way to explain how to choose between “its” and “it's”. We could keep this one here open as a canonical question, but it would have to be edited in shape first. In any case, it might be too broad. – RegDwigнt May 1 '11 at 20:09
@Matt Ellen, alien's ship (I don't mean: alien is ship) and aliens's ship (the same) are correct? I'm suprised! Extra question: can I say "aliens' ship" instead of "aliens's ship"? – daGrevis May 1 '11 at 20:18
up vote 1 down vote accepted

I'll paste an answer I wrote some time ago.

It's called "Saxon genitive"; the general rule is that you use it after people/animals/things and never with adjectives or with personal pronouns (you'd never say "this is he's car", since "he's" always means "he is".

In this case you would use the possessive pronouns his, her, theirs, etc.

Plus, if the noun is plural you can say "Aliens' ship".

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