Plurals
Q. While reviewing the 15th edition of CMOS, I believe I noticed a proofreading error under 7.16 (page 281). This entry shows apostrophes with M.A.’s and Ph.D.’s, then adds the following: (or MAs and PhD’s). Shouldn’t MA’s also have an apostrophe? Please let me know if my deduction is correct or if I’ve misunderstood the rule.
A. Although we must confess to occasional typos in CMOS, section 7.16 is correct. We omit the apostrophe when there are no periods in an abbreviation (MAs), but use it when an abbreviation has periods (M.A.’s) or internal capitalization (PhD’s).
