I am just used to thinking of everyone without a title as a knight. I have always considered nobles to be knights, just not knight of such and such. However Stabbity is right, the game never calls them such.
Yeah, I mean I always call landless nobles knights too (sometimes Lord depending on the person) but I mean actually being knight of a region, with the title, without having an estate. It doesn't seem like it should be difficult to code, at least not if being able to become a knight of a region by being in the same region of the lord is possible. The main purpose would be for nobles who don't gold (rich people and priests) to be able to be in a knight of a region, without having to take 5% from other people needlessly when they don't have much of a desire for it.
