Hardness
A material's resistance to localized plastic surface deformation induced by mechanical scratching, abrasion, or indentation.
Governing formula
H = Load / Indentation Surface Area (Mohs, Vickers, Rockwell)
SI unit
MPa or GPa (Mohs scale 1 to 10)
In depth
Hardness correlates with yield strength and interatomic bond strength. Measured using standardized indentation tests (Vickers, Rockwell, Brinell) or Mohs relative scratch scale (1 for talc to 10 for diamond).
Examples in the real world
Tungsten carbide and industrial diamond cutting tools machining hard steel alloys.