An it's needs an apostrophe when it's saying "it is". And it's needs an apostrophe when it's signifying ownership, like Jenny's or Paul's. Now, I know there must be, but I can't for the life of me think of another use of the word it's where there is no apostrophe. Isn't there one? I could swear I remember being taught the difference, but....can't ever remember doing it. Can someone refresh my memory before I go insane?