Tatiana Ayazo/Rd.com

Brother-in-laws, runner-ups, hole in ones, etc.

What you actually mean: Brothers-in-law, runners-up, holes in one, etc.

Plurals of these compound nouns are formed by adding an “s” to the thing there’s more than one of (brothers, not laws). Some exceptions: words ending in “-ful” (mouthfuls) and phrases like culs-de-sac. On the other hand, it’s hard to believe these irregular plurals are actually correct.

