The apostrophe is a punctuation mark, and sometimes a diacritical mark, in languages that use the Latin alphabet or certain other alphabets. In English, it serves three purposes:
- The marking of the omission of one or more letters (as in the contraction of do not to don’t).
- The marking of possessive case (as in the cat’s whiskers, or in one month’s time).
- The marking by some as plural of written items that are not words established in English orthography (as in P’s and Q’s). (This is considered incorrect by others; see Use in forming certain plurals. The use of the apostrophe to form plurals of proper words, as in apple’s, banana’s, etc., is universally considered incorrect.)
- The “Possessive” Apostrophe (englishtutoronlineusa.wordpress.com)
- Oh No! It’s The Apostrophe Catastrophe! (chrishorstman.wordpress.com)
- IELTS Writing Task 1 and Task 2 Tips: apostrophes (oxbridge-english.com)
- Apostrophe Catastrophe (conversationallyspeaking.wordpress.com)