Possessives and Attributives

Q. I have suddenly become an editor and am having trouble on a daily basis with the numeric use of decades. First, is “the 90s” or “the ’90s” correct? We often see the apostrophe omitted these days. Next, if a sentence contains the phrase, “Perhaps the 70s best director . . .” (meaning, the best director of that decade), “70s” is both plural and possessive. Should it be “70’s”? “70s’”? Other than reconstructing the sentence, what’s an editor to do?

A. Strictly speaking, ’90s, with the apostrophe, is correct.

The ’70s’ finest director was Martin Scorsese, particularly for his work on Alice Doesn’t Live Here Anymore and Taxi Driver.

Note the apostrophes, both of them. You are always free to write “seventies’ finest.” Or, “The finest director of the ’70s was assuredly Francis Ford Coppola, for his work on the first two Godfather films and Apocalypse Now.

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]