lack、want、absence、shortage与scarcity这些名词均含“缺乏、不足”之意。
lack : 普通用词，指部分或完全的不足。
Her only problem is a lack of confidence.
她唯一的问题是缺乏自信。
Lack of sleep had made him irritable.
睡眠不足令他烦躁易怒。
If he fails it won't be for/through lack of effort (= he has certainly tried).
他若失败了，那肯定不是因为他努力不够。
We won't be going away this year - lack of funds, I'm afraid.
今年我们恐怕不会去度假了——因为没钱。
want : 指完全或短缺某物，侧重缺少之物是必需的东西。使用范围比lack窄些。
For want of anything better to do I watched television for a while.
由于没有什么更好的事情可做，我就看了一会儿电视。
If we fail it won't be for want of trying (= we have tried even if we fail).
即使我们失败了，我们也曾努过力。
absence : 指某物根本不存在或完全短缺，或某人虽存在，但未到现场。
A new manager was appointed during/in her absence.
她不在的时候任命了一位新经理。
She has had repeated absences from work this year.
今年她屡次旷工。
shortage : 指不足，但侧重达不到规定的，需要的或已知应有的数量。
There's a shortage of food and shelter in the refugee camps.
难民营里缺少足够的食物和住处。
The long hot summer has led to serious water shortages.
这个夏天漫长而炎热，导致严重缺水。
scarcity : 指产量不足或缺乏某物难以应付或满足需要。
the scarcity of skilled workers
缺乏熟练工人