c. 1200, transitive, "make (something) hard," from hard (adj.) + -en (1). Intransitive meaning "to become hard" is late 14c. The earlier verb was simply hard, from Old English heardian. Related: Hardened; hardening.
实用例句
1. Give the cardboard two or three coats of varnish to harden it.
在纸板上涂两三层清漆使其变硬。来自柯林斯例句
2. Their action can only serve to harden the attitude of landowners.
他们的行动只会让土地拥有者的态度变得更坚定。来自柯林斯例句
3. The varnish takes a few hours to harden.
清漆需要几个小时才能干透。来自《权威词典》
4. Hot steel is quenched to harden it.
烧热的钢放入水中骤冷使之坚硬.来自《简明英汉词典》
5. Test to see if the finish is tacky, and if it is, leave it to harden.
