Basically, hardness is the ability of a material to resist indentation, penetration or scratching caused by another material. The larger the area produced by a given force, the lower the hardness. Strength = Stress required to produce failure. The difference between strength and hardness is that the strength refers to the force that is present between the bonds. The terms are also very frequently encountered when shopping for 3D printing filaments. It is often used to determine how much force an object can take without breaking, but there are many measures of strength. When discussing any material – whether it’s plastic, metal, or a composite – a distinction is often made between hardness, toughness, and strength. While strength is the property of the solid, hardness is not one property of solid as the later one is measured with respect to or relative to another material. Hardness, on the other hand, is defined as the ability to resist deformation. Hardness = Force / Area. Strength attributes to how strong or … To the common consumer, these terms sound very similar. It can be correlated to, but is not the same as strength. Strength is defined as the ability to withstand an applied load without failure. Increase one and the other follows suit. But even though the two are different, they are also directly related.