The apostrophe has a tortured existence. As ①it is used most commonly to indicate possession or show where a letter or number is missing, its correct use has caused so much confusion that some people have called for ②it to be removed from the English language. Others, unsure of' when to use ③it and when not to, make a choice for non-use, perhaps in the hope that no one will notice. It is essential for the *contraction. And in ④it, two words are combined into one, as in don't, can't, and aren't. ⑤It has similar function in short forms of numbers, such as writing '05 for 2005. *contraction : (말이나 글의) 단축(형)