decrease : 指逐渐地、不断地减少。
- Our share of the market has decreased sharply this year.
- We have decreased our involvement in children's books.
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.
- These memories will not be diminished by time.
- What he did has seriously diminished him in many people's eyes.
- We've seen our house diminish greatly/sharply/substantially in value over the last six months.
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.
- The noise began to lessen.
- 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?
- The plane reduced speed as it approached the airport.
- My weight reduces when I stop eating sugar.
- We bought a TV that was reduced from £500 to £350 in the sales.
- I reduced the problem to a few simple questions.
- The community has dwindled to a tenth of its former size in the last two years.
- Her hopes of success in the race dwindled last night as the weather became worse.