Q. Hi. In Chicago Style, are “T” and “F” acceptable for “True” and “False”? The document is simple questions with T and F answers.
A. If you mean capital letters T and F without periods, then yes. Chicago style requires periods with initials in names—as in “F. Scott Fitzgerald” and “T. S. Eliot”—but not with other types of capitalized initialisms (most of which include at least two letters, as in “US”; see CMOS 10.4). And though the abbreviations for t defined as “true” and for f defined as “false” are lowercase as main entries in Merriam-Webster—where other meanings range from “metric ton” to “folio” and “full”—a “Kids Definition” farther down the page for each entry capitalizes T and F to mean “true” and “false,” suggesting their common use in quizzes and tests. For spelling out abbreviations on first use, see CMOS 10.3.