Subscribe to The Chicago Manual of Style Online
Possessives and Attributives
Q. I understand CMOS’s position on this, but I need help with my argument. Our company’s acronym is singular and ends in an S, just like CMOS. I want to write it with an apostrophe s when needing possession, but others want to use only the apostrophe, as in CMOS’. I need help with my argument with my boss. Thank you.
A. Unlike a personal name that ends in an s (e.g., Harris), an all-caps acronym like CMOS (pronounced SEE-moss) doesn’t even have the appearance of a plural; the s that signals a plural ending is normally lowercase. (A company with two chief marketing officers would have two CMOs, not two CMOS.) So even if you followed a style that prefers Harris’ reputation to Harris’s reputation, an expression like TASS’ headquarters (for the Russian news agency) would risk being misread, whereas TASS’s headquarters is perfectly clear. The same could be said for an initialism, which is pronounced as a series of letters: CBS’s newscasts is more clearly possessive than CBS’ newscasts. We sincerely hope you manage to win your argument (and keep your s).