hardnessindex
nounUK /ˈhɑːdnəs ˈɪndɛks/
US /ˈhɑːrdnəs ˈɪndɛks/
A number that tells you how hard something is.
The hardness index of the diamond was very high.
OTHER MEANINGS
2. A measure used in materials science to compare how resistant materials are to scratching.
Engineers checked the hardness index of the new metal alloy.
3. A value in water testing that shows how much calcium and magnesium is in the water.
The water's hardness index was high, so they installed a softener.
4. A rating used in food science to describe how firm or tough a food feels.
The hardness index of the apple helped farmers decide when to pick it.