Yes, they can be thought of as categories. So 'class' or 'type' are appropriate. My point was simply that if a term is so awkward you have to explain the choice to your audience to avoid confusion, you probably could've chosen a better term--all the moreso if you're just parroting something someone else parroted from Google Translate. The original JP itself probably isn't even an official term, and therefore there's no obligation to be faithful to it.