这些动词的共同含义是“减少，变少”。
decrease : 指逐渐地、不断地减少。
- Our share of the market has decreased sharply this year.
今年我们的市场份额急剧下降。 - We have decreased our involvement in children's books.
我们减少了在儿童读物方面的投入。
diminish : 侧重大小数量和重要性的不断减小，强调减小的部分。
- I don't want to diminish her achievements, but she did have a lot of help.
我不想贬低她的成就，但她确实得到了很多帮助。 - These memories will not be diminished by time.
这些记忆不会随着时间的流逝而淡漠。 - What he did has seriously diminished him in many people's eyes.
他的所作所为严重损害了他在许多人眼里的形象。 - We've seen our house diminish greatly/sharply/substantially in value over the last six months.
在最近6个月里，我们这座房屋的价格暴跌。
lessen : 普通用词，与decrease近义。指数目、程度、价值、实力等的减少。
- A healthy diet can lessen the risk of heart disease.
健康饮食能降低患心脏病的危险。 - The noise began to lessen.
噪音开始减弱。 - to lessen the risk/impact/effect of sth
减少某事物的风险 / 影响 / 效果
reduce : 普通用词，含义广。指数量、程度的降低或减少。
- Do nuclear weapons really reduce the risk of war?
核武器真的可以减小战争爆发的危险吗？ - The plane reduced speed as it approached the airport.
当飞临机场时，飞机减慢了速度。 - My weight reduces when I stop eating sugar.
我停止吃糖时体重就会下降。 - We bought a TV that was reduced from £500 to £350 in the sales.
我们在大减价时，买了一台从500英镑减至350英镑的电视。 - I reduced the problem to a few simple questions.
我把这个难题简化为几个简单的小问题。
dwindle与decrease同义，指逐渐减小，但强调变得越来越少终至全无。
- The community has dwindled to a tenth of its former size in the last two years.
该社区在过去的两年里缩小到了原来的1/10。 - Her hopes of success in the race dwindled last night as the weather became worse.
随着昨晚天气的恶化，她在比赛中获胜的希望减小了。
