More hard than medium for me but thoroughly enjoyed solving it (with a bit of help from mr Google!!)

Duh, you did have it as hard!!

I enjoyed this one and there were some nice overlaps. I would rate it closer to medium than hard. One thing that would raise the difficulty level is if the mass/plural nouns group interacted with one of the other categories (probably the bones). Of course, maybe it does and I just didn't realise. Good work.

Some good puzzles here which wa enjoyable. Being pedantic, corps isn’t not strictly speaking in the plural in the way that the other ones in the group are (the s is a result of its French derivation - it’s not a grammatical plural).