I'd say this is a fiendish one. Some very good but very obscure groups!

Def fiendish due to excellent red herrings ty

I have to apologize for mislabeling the difficulty here! I've just started making my first puzzles! I'm glad people can enjoy them, at least, and please let me know if there is a good way to edit the difficulty ratings after publishing. There doesn't seem to be an option to do that -- hopefully the site factors difficulty feedback in and adjusts as needed?

The Greek one can also all end in gram

Y -- Thank you! Updated to accept "gram"; also now should accept answers of "numeral" and "number"