Help with information architecture vocabulary

So, I'm trying to expand my information architecture vocabulary in english and I'm struggeling with tags.

Lets say I want to describe a product with a couple of keywords. I've desided that you could describe it by color (blue, red or green), size (small, medium or big) and material (stone, plastic or steel).

To me Blue or Small or Stone are tags. But what do you call Color, Size and Material with a common name? A Tag category? A Tag group? Or is stone an attribute of the tag Material? Or should I talk about just categories and values instead?