1.weaken可指生物体表明健康状况的官能效果丧失、体力衰弱,也可指物质或非物质的完整性、稳定性、强度、数量等方面减弱或丧失。引申可指“(使)犹豫”。
2.weaken既可用作不及物动词,也可用作及物动词。用作及物动词时,接名词或代词作宾语。

用作不及物动词
▲S+～(+A)
His strength has weakened.他的体力下降了。
She weakened as the illness grew worse.由于病情恶化,她变得更弱了。
The enemy's attacks weakened.敌人的攻击减弱了。
They have not yet agreed to our requests but they are clearly weakening.他们还没有同意我们的要求,但态度已明显软化。
用作及物动词
▲S+～+n./pron.
The strain of the last few days has weakened her considerably.最近几天的劳累在很大程度上使她身体衰弱了。
The illness weakened his heart.疾病使他的心脏衰弱了。
You can weaken the tea by adding water.你可以加水把茶弄得淡一些。
None of these setbacks could weaken her resolve to become a doctor.这些挫折一点也动摇不了她要当医生的决心。