Its is the possessive form of it. it's (with an apostrophe) is always short for it is (it's so fun) or it has (it's been nice knowing you). But, you might ask, don't apostrophes show possession, as in teacher's. The rule is actually pretty simple:

It's raining means it is raining; It's been warm means it has been warm. It's vs its is one of the most common english grammar mistakes made. Its (no apostrophe) is the possessive form of the pronoun it. Most possessives use an 's, which is probably the reason that. How do we easily tell the difference between it's and its? The simple trick is to expand the contraction it's to either it is or it has and see if the sentence still makes sense.

Most possessives use an 's, which is probably the reason that. How do we easily tell the difference between it's and its? The simple trick is to expand the contraction it's to either it is or it has and see if the sentence still makes sense.