Apostrophe

The apostrophe (’, ') is a punctuation mark, and sometimes a diacritical mark, in languages that use the Latin alphabet and some other alphabets. In English, the apostrophe is used for two basic purposes:

• The marking of the omission of one or more letters, e.g., the contraction of "do not" to "don't"
• The marking of possessive case of nouns (as in "the eagle's feathers", "in one month's time", "the twins' coats")

It is also used in a few exceptional cases for the marking of plurals, e.g., "p's and q's" or Oakland A's. The same mark is used as a single quotation mark. It is also substituted informally for other marks – for example instead of the prime symbol to indicate the units of foot or minutes of arc. The word apostrophe comes from the Greek ἡ ἀπόστροφος [προσῳδία] (hē apóstrophos [prosōidía], '[the accent of] turning away or elision'), through Latin and French.