Like all of you, I’ve spent this long week noticing the glaring disagreement in how various media outlets apply apostrophes to the current situation with Chicago’s teachers. Is it “teachers union”—per the Sun-Times, the Tribune, and WBEZ, not to mention the Chicago Teachers Union—or “teachers’ union,” per us? (Also the Chicago Manual of Style and the New Yorker.) A couple years ago on the Columbia Journalism Review language blog, Merrill Perlman wrote that AP style counsels against applying an apostrophe to nouns before other nouns if they appear “primarily in a descriptive sense”: “citizens band radio, a Cincinnati Reds infielder, a teachers college, a Teamsters request, a writers guide.”

Chicago, on the other hand, acknowledging that “the line between a possessive or genitive form and a noun used attributively . . . is sometimes fuzzy,” recommends an apostrophe, only ditching the mark in proper names—like Chicago Teachers Union.

You may go back to your regular news reading now.