Hardness (of stone, steel and the like); rigidity, firmness;
The hardness of this bread is like a rock now.
ngaN-/N-, pa-, ma-, sika-
To become hard [ngaN-]; to increase in hardness [pa-]; to make s.t. hard.
The -an/pa--un imp. focuses on the whole object being hardened (usually temporarily). The pa--an imp. focuses on the object being changed to make it permanently hardened.
If cooked rice has been left out for a night, for sure it will become hard.
Make the mixture for those pastries thicker (lit. harder).
That guy and I were making it hard on each other when running a race.