hardness

These alloys are characterized by their extreme hardness.

这些合金的特点是具有极高的硬度。

The hardness of his life stemmed from the chronic poverty into which he was born.

因为他生于长期贫困的家庭，所以生活艰难。

He was angered at their hardness of heart.

他对他们的冷酷无情感到愤怒。