Most people just don't care whether or not they put an apostrophe when it's needed [see, I just used one!], simply because they don't know IF they need it.
When should you use an apostrophe?
You should use an apostrophe if you are OMITTING a letter, in this case, "It is ..." gets shortened to, "It's" - you leave out [omit] the second "i", and it gets replaced with an apostrophe:
It's = It is = It has = It was
- It's [it is] raining men!
- It's [it is] a long way to Tipperary!
- It's[it is] just not fair - I should have first prize.
- I liked that movie - with all its adventure, It's [it is] going to be a smash hit!
- Isn't it a shame? Yes It's [it is] a shame we missed the train.
- It's [it has] been such a great week.
Its = Its *own* ... *no* apostrophe
When do you use "Its" without an apostrophe?
You don't need an apostrophe if you want to say:
(a) The cat licked its fur.
If you had an apostrophe in this phrase, you'd be saying:
The cat licked it is fur.
You don't want to say that, do you? No, I didn't think so.
(b) The briefcase and its contents were stolen.
If you put an apostrophe in this sentence, it would mean you meant to say:
(b) The briefcase and it is contents were stolen.
You don't *really* want to say that, do you? Of course not.
I hope this helps.
If in doubt, don't!
What do I mean by that? Well, if you're not sure, don't use an apostrophe.
You *only* need an apostrophe if you REMOVE or OMIT a letter in "it is"[or to show possession or ownership].
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