Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
PERIOD 1
This punctuation mark (.) is used to indicate the ends of sentences or sentence fragments that do not use question marks or exclamation points. Conventionally it occurs at the ends of some abbreviations, after numbers and letters that indicate the items in lists of outlines, and after initials in a person’s name; in some stylebooks, periods are specified as the punctuation in act, scene, and line references (II.iii.45–48) and the like. See also ELLIPSIS (3).
