apostrophe s showing possession

[atabitaraf]

My question is that: Must we use "apostrophe s" just for humans or maybe animals? or we can use it for objects too?

Dubious Rule: for humans we can use "apostrophe s" for showing possession but for objects we shoud say "s.th of s.th" or "s.th s.th" without "apostrophe s" so we say:
eg1. John's book.
eg2. The door of the house.
eg3. The house door.

[Rover_KE]

For people and animals apostrophe s is fine.

For inanimate objects it's not as clear cut.

The tree branch is normal, but so is the tree's leaves. (The tree leaves sounds odd.)

The car windows are open is good, but if more than one car is involved, it's the cars' windows are open.

Go figure.

Rover

[SoothingDave]

I would say "my car's paint is peeling" not "my car paint."

[emsr2d2]

I would say "my car's paint is peeling" not "my car paint."

So would I. But then I would go out and buy a can of "car paint".

[atabitaraf]

Do you mean that for objects we can't make any gramatical rule?

[bhaisahab]

So would I. But then I would go out and buy a can of "car paint".

I would say "The paint on my car", I can't imagine ever saying "My car's paint" it doesn't sound natural to me.

[Rover_KE]

Do you mean that for objects we can't make any grammatical rule?

That's right: we can't.

Rover

[atabitaraf]

What would be the rule about objects? Thanks,

[Rover_KE]

There is no rule.

[Chrystalline]

No, there is a rule. "My car's paint" may sound unnatural to you, but it is perfectly legitimate. Perhaps it is uncommon in your area; every region is subject to preferences in phrasing and word choice.

The distinction between the tree branch and the tree's leaves is that, in the first phrase, "tree" is an adjective describing the noun "branch." Only the second uses the possessive. The same applies to the following:

The car windows are open is good, but if more than one car is involved, it's the cars' windows are open.

The difference is whether you're using the possessive or simply describing an object.

The only exception to the use of apostrophes for possessives is the word "its," because in that case, the apostrophe indicates the contraction for "it is."

It's = it is
Its = belongs to it