In linguistics, we have “open and closed wordclasses”. The exact same thing exist in ludemes for game design but I don’t known the word for it. Alex lists some examples for D&D style games in this post:

The Milliwhack metric for campaign lethality. I’ve lost track. What usually happens with D&D is that the lethality is higher in the lower levels of the campaign. Which is pretty appropriate & good design 🤷🏻‍♀️