1. vt. & vi.（使）变坚硬，（使）变坚强，（使）坚定　 (cause sth) become hard, strong, unyielding, etc.
2. vt.使麻木不仁或毫不在乎　 make sb less sensitive (to sth)

　～ the body　锻炼身体
　～ one's heart　心肠变硬
　～ steel　淬火
　～ considerably　很坚硬
　～ utterly　非常坚定
　～ in　拉紧
　～ off　使长壮以移植户外
　～ up　变得坚实
　～ into　凝固成
　～ to　对…变得无动于衷
　～ toward　对…冷酷无情

　Clay hardens when it becomes dry.　黏土干了的时候就变硬了。
　The soft concrete will harden till it is like stone.　水泥将变硬直到像石头一样。
　The varnish takes a few minutes to harden.　清漆几分钟就变硬了。
　The snow hardened until ice was formed.　雪变成冰后就会硬。
　Attitudes to the strike have hardened on both sides.　双方对罢工所持的态度更加强硬了。
　Opposition to the military government hardened after the massacre.　大屠杀后，反对军政府的力量更强硬了。
　He hardened his hold on the door.　他更加使劲地抓住门。
　Life in the mountains hardened me.　山区的生活使我更加坚强。
　Don't harden your heart against him.　不要对他冷酷无情。
　For her good, You must harden your heart.　替她着想，你不能心软。
　Doctors are hardened to the sight of blood.　医生看见血无动于衷。
　He had utterly been hardened by all shame.　他毫无廉耻之心。

 ♣ harden in　(v.+adv.)
　绷得紧　stretch sth tight
　You'd better harden in the ropes, the sails are not tight enough!　你最好拉紧大绳，帆绷得还不够紧。
 ♣ harden into　(v.+prep.)
　凝固成　change sth into sth because of coldness
　Lava as it cools hardens into rock.　岩浆冷却后凝成岩石。
　Harden one's revolutionary will into steel.　把革命意志锻炼得钢铁般坚强。
 ♣ harden off　(v.+adv.)
　使耐寒以备室外种植　become hard, ready for planting outside
　When the onion plants have hardened off, we can plant them in the garden; they should be ready soon.　洋葱苗长壮后，我们就可以把它们移植到菜园里；这些苗很快就可以移植。
　What is the best way to harden off new rose bushes only a few inches high?　要想使只有几英寸高的玫瑰长壮以移植户外，什么办法最好?
　Potted plants should be hardened off before planting out.　盆栽植物应经耐寒锻炼才能移植到室外。
 ♣ harden to　(v.+prep.)
　对…变得无动于衷　make sb less sensitive
　He hardened early to a life of crime.　他很早就习惯了犯罪生涯。
　Do you think that John is becoming hardened to failing his driving test?　你是不是认为约翰对驾照考试的失败已麻木了?
　Poor people often become hardened to suffering.　穷人常常变得能忍受苦难。
　They've been hardened to the horrors of war.　他们对战争的恐怖已无动于衷了。
　He became hardened to the suffering around him.　他对周围的苦难现象已见怪不怪了。
 ♣ harden toward　(v.+prep.)
　对…冷酷无情　be cold to sb
　His heart hardened toward his nephews.　他对他的侄子们心肠很硬。

 ♣ harden, cake, indurate, petrify, solidify
　这组词都有“使变硬或凝固”的意思。它们的区别是：harden强调变硬的过程或结果；cake指凝结成坚硬的块状物；indurate指使原来坚硬的东西更加坚硬或结实；petrify指动植物石化或变得像石头一样坚硬；solidify强调最终发生质的变化。