What is the definition of hardness?

In materials science, hardness refers to the "characteristic of a solid material to resist permanent deformation."

The ability of a material to locally resist a hard object pressing into its surface is called hardness.

The local resistance of a solid to the intrusion of external objects is an indicator for comparing the softness and hardness of various materials.

Due to the stipulation of different testing methods, there are different hardness standards.

The mechanical meanings of various hardness standards are different and cannot be directly converted to each other, but they can be compared through testing.