Two days after changing its style on the term "illegal immigrant," the Associated Press issued a Stylebook update that's significant but in a much quieter way:

One word in all uses.

OK, it's a big deal mostly to copy editors, many of whom have spent a good part of their professional lives jamming a space into "underway."

Here's the old listing:

under way Two words in virtually all uses: The project is under way. The naval maneuvers are under way.

One word only when used as an adjective before a noun in a nautical sense: an underway flotilla.

I surveyed a few copy-editing icons on whether the AP switch would occasion one at their organizations:

• "Nothing in the works at this point," New York Times Associate Managing Editor for Standards Philip Corbett writes in an email to Poynter.

• "Probably," writes John McIntyre of The Baltimore Sun. "We minimize our exceptions to AP style, and the stylebook editors are correct that their ruling is consonant with what the dictionaries find to be common usage."

• "The Post has used the one-word form forever," The Washington Post's Bill Walsh writes. He followed that email with forensic analysis comparing occurrences of "under way" vs. "underway" in the Post until 1990, which he thinks indicates the paper made the change in 1989. Here's his research, which I made into a chart:

"The numbers could be skewed by 'underway flotillas,' of course, but I can't imagine it's by much," Walsh writes. "I'm not sure I've ever seen that usage outside a stylebook."

Here are some tweets I found about the change: