1. the quality or state of being firm, solid, or resistant to pressure
2. difficulty or severity in conditions or circumstances
3. lack of compassion or kindness; cruelty

Examples

• The hardness of the diamond made it perfect for cutting tools.
• We tested the hardness of different metals in science class.
• The hardness of winter made survival difficult for the settlers.
• His hardness toward his employees made him unpopular.
• The rock’s hardness was measured using the Mohs scale.
• She was surprised by the hardness of his voice when he spoke.
• The hardness of the economic times forced many businesses to close.