weakness
词根词缀：
bitterness n. 辛酸；苦味
bitter 苦的 + ness 性质，状态 → 辛酸；苦味
brightness n. 光明
bright 光明的 + ness 性质，状态 → 光明
emptiness n. 空洞
empty 空的 + ness 性质，状态 → 空洞
kindness n. 仁慈
kind 仁慈的 + ness 性质，状态 → 仁慈
positiveness n. 肯定
positive 肯定的 + ness 性质，状态 → 肯定
promptness n. 敏捷，迅速
prompt 迅速敏捷的 + ness 性质，状态 → 敏捷，迅速
weakness n. 虚弱；弱点
weak 虚弱的 + ness 性质，状态 → 虚弱；弱点
数据来源：新东方英语词汇速记大全
相关例句：
He admitted his weakness.
他承认自己的短处。
Narrow-mindedness is an old weakness of mine.
气量狭窄是我的老毛病。
Carelessness is an old weakness of his.
粗心大意是他的老毛病。
The Treasury had been blaming the pound's weakness on the backwash from the falling dollar.
财政部一直将英镑的疲软归咎于美元贬值。
A tiny insect, trying to shake a mighty tree, is ludicrously ignorant of its own weakness.
蚍蜉撼大树，可笑不自量。
Drinking is his weakness.
他的缺点是爱喝酒。