This bread has just the right firmness.
金属の硬さを測る。
Measure the hardness of the metal.
honesty; integrity; uprightness
Only when written 堅さ
Metaphorical use referring to a person's character: being principled, honest, or unwavering. Often written 堅さ in this sense.
彼の堅さは誰もが認めるところだ。
Everyone acknowledges his integrity.
We measure the hardness of this rubber.
As it cooled, the chocolate became harder.
Perhaps out of nervousness, his expression showed some stiffness.