Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
APOSTROPHE 2
is the mark of punctuation (’) used (1) to indicate a missing letter or letters, as in contractions such as isn’t, they’re, and it’s, (2) to distinguish genitives of nouns from noun plurals not in the genitive (boy’s, boys’, but plural boys), and (3) sometimes to mark plural numbers and letters (three 6’s, two A’s). Never use an apostrophe in front of the -s ending that forms a plural noun (The sign says Fine Meal’s), in front of the -s that forms a third-person singular present tense verb (Accused Plead’s Insanity), or before the -s in an absolute possessive pronoun (This hat is her’s). Apostrophes appearing where they ought not to be or missing from where they ought to be are devastating shibboleths in the view of many Standard users, who will penalize the perpetrators mercilessly for them regardless of whether haste, inadvertence, or ignorance caused the outrage against convention. Be warned. See ITS.
