hard

固(かたい)	Hard like firm, unyielding, you tap it and it goes TON TON. Also, hard like a stiff, formal, tight-ass person. $$$

硬(かたい)	Almost the same as 固 – but the nuance is, hard like hard to break.

堅(かたい)	FIGURATIVE: hard as in a steadfast, Sam Gamgee-ass pal.