The apostrophe (ʼ) is not usually considered part of the English alphabet nor used as a diacritic, even in loanwords. But it is used for two important purposes in written English: to mark the "possessive" and to mark contracted words. Current standards require its use for both purposes. Therefore, apostrophes are necessary to spell many words even in isolation, unlike most punctuation marks, which are concerned with indicating sentence structure and other relationshi…