Help need apostrophe advice

[peoplepleaser1]

I'm proofing something I've written and need to send before midnight.

I thought I was clear about the correct use of apostrophes but I'm not sure about wether an apostrophise is needed in the 'its' in the following sentence:

A cat's nap is often the highlight of its day.

I want to put it's because the nap belongs to 'it' but then it looks a bit like I'm incorrectly putting in an omission apostrophe for 'it is'.

Can anyone help please?

@mutantdisco - you have just succinctly said what it took me a great deal more to say

@How2Help - V often an apostrophe is a shortening so Who's is Who is , or Who was. Whose is a possessive thing.

So ( and I do think we need an MN cat here as they have been kind enough to lend themselves )

So - and please an English teacher help me here as I am dredging from long ago

Cat - who's licking his white paws - "Who is licking his white paws" "apostrophe"
Cat - Whose owner is watching him licking his white paws - Whose as possessive. ( word , not owner)

I really want to see this cat now

Who’s isn’t a shortening of who was.

Thank you. That makes sense. I think I had in my head possesive things always had an apostrophe. This is all much clearer now.

I went to school, honest. Not sure what I learnt though

@IhateBoswell - You are right and I am wrong - it is who is or who has. Apologies. It was quick typing but you are right. Gosh I hope am right now - but yes - good to point that out. Thank you .

I'll make it simple.

It's is always short for it is, or it has.
It's raining, it's been snowing, etc. (It is raining, it has been snowing.)

So if it doesn't mean it is, or it has, it doesn't need an apostrophe.

It would seem logical for the possessive its (the dog is in its bed) to have an apostrophe, but it doesn't.

OP here....

Thank you so much to everyone who has helped me with this.

I'm not sure why but I was unaware of the exception relating to possessive pronouns. Somehow I hadn't really given it much thought until last night .

This thread has been informative, kind and funny- mumsnet at its best.

Thanks again.

@BasiliskStare, no on the contrary, you've been very helpful. Thanks