It’s a compound noun and in those cases, we generally make the principal word plural.
An attorney general is an attorney, not a general. So “attorney” is the principal word, and an “s” is added to that to indicate plural form, “attorneys general.”
Take the term “daughter-in-law”, another compound noun. “Daughter” is the principal word. If you have two relatives, they are daughters-in-law, not daughter-in-laws.
More info here: [https://www.myenglishpages.com/grammar-lesson-plural-compound-nouns/](https://www.myenglishpages.com/grammar-lesson-plural-compound-nouns/)
Latest Answers