Hardness is a property that describes how resistant a material is to scratching or denting. Hard materials do not easily change shape when pressure is applied. Softer materials can be scratched or marked more easily. Hardness is used to compare different materials.

Hardness is observed in natural materials like minerals and rocks, and in manufactured materials like metals. It is used to help identify substances. Tools and objects are often chosen based on their hardness. This property is important in many everyday materials.