不及物动词：decline; decrease; diminish; drop; dwindle;
及物动词：decrease; diminish; reduce; lessen;
Decline : （不及物动词）To deteriorate gradually; fail.逐渐恶化；衰败 His health /influence has begun to ~ as he is older. The global economy is declining recently.
The market for this product has declined.
Decrease : （及物动词）1.To grow or cause to grow gradually less or smaller, as in number, amount, or intensity.
减少：在数目、数量或强度方面逐渐变得或使…变得少或小, （及物动词, 后接可数名词）
The workmen want to decrease the number of working hours and increase pay.
工人要求减少工作时间而增加工资。
to decrease the number of working hours; to decrease traffic accidents.
2. 不及物动词:
Our sales are decreasing.
Spending has decreased slightly.
Diminish: （及物动词）1. To make smaller or less or to cause to appear so. 减少：使减少或使似变少
a. His illness diminished his strength.他的病削弱了他的体力。(主语, 宾语皆为抽象名词)
b. An occasional outburst didn't diminish my respect for her. 偶尔的一次发火并未减少我对她的尊敬。
2. （不及物动词）To become smaller or less.
The warden's authority diminished after the revolt. (主语为抽象名词) 典狱长的权威在动乱后下降了。
However, my enthusiasm waned. The time I spent at exercises gradually diminished . 然而，我的热情减退了。我在做操上花的时间逐渐减少了
Drop : （不及物动词）To cause to become less; reduce:使减少： drop the rate of production.降低生产率
（不及物动词）Prices / interest rate dropped. 价格/利率降低了。
Dwindle:1. 不及物动词）To become gradually less until little remains. 逐渐减少：逐渐地减少直到所剩无几. Dwindle suggests decreasing bit by bit to a vanishing point:
Dwindle 含有一点一点减少直到消失的意思
Their savings dwindled away. 他们的积蓄一点点地消耗殆尽了。
Lessen 1.v.tr.（及物动词）To make less; reduce.使变小；使减少 Use your seat belt to lessen the danger of injury in an accident.系上座椅安全带，减少交通事故中受伤的危险。(宾语为抽象名词) e.g. to lessen hazard, to lessen anxiety
2.v.intr. （不及物动词）To become less; decrease
His appetite lessens as his illness progresses. 随着病情的加重，他的食欲下降了。(主语为抽象名词)
Reduce : （及物动词）To bring down, as in extent, amount, or degree; e.g.1.They've reduced the prices in the shop, so it's a good time to buy.商店已经降低了商品的价格，看来现在是买东西的好时候。
2. The fire reduced the forest to a few trees.
Reduce emphasizes bringing down, as in size, degree, or intensity: Reduce 强调在大小、程度或强度方面下降或减少：
The workers reduced their wage demands.
工人们降低了他们在工资方面的要求。
不及物动词：decline; decrease; diminish; drop; dwindle;
及物动词：decrease; diminish; reduce; lessen;
Decline : （不及物动词）To deteriorate gradually; fail.逐渐恶化；衰败 His health /influence has begun to ~ as he is older. The global economy is declining recently.
The market for this product has declined.
Decrease : （及物动词）1.To grow or cause to grow gradually less or smaller, as in number, amount, or intensity.
减少：在数目、数量或强度方面逐渐变得或使…变得少或小, （及物动词, 后接可数名词）
The workmen want to decrease the number of working hours and increase pay.
工人要求减少工作时间而增加工资。
to decrease the number of working hours; to decrease traffic accidents.
2. 不及物动词:
Our sales are decreasing.
Spending has decreased slightly.
Diminish: （及物动词）1. To make smaller or less or to cause to appear so. 减少：使减少或使似变少
a. His illness diminished his strength.他的病削弱了他的体力。(主语, 宾语皆为抽象名词)
b. An occasional outburst didn't diminish my respect for her. 偶尔的一次发火并未减少我对她的尊敬。
2. （不及物动词）To become smaller or less.
The warden's authority diminished after the revolt. (主语为抽象名词) 典狱长的权威在动乱后下降了。
However, my enthusiasm waned. The time I spent at exercises gradually diminished . 然而，我的热情减退了。我在做操上花的时间逐渐减少了
Drop : （不及物动词）To cause to become less; reduce:使减少： drop the rate of production.降低生产率
（不及物动词）Prices / interest rate dropped. 价格/利率降低了。
Dwindle:1. 不及物动词）To become gradually less until little remains. 逐渐减少：逐渐地减少直到所剩无几. Dwindle suggests decreasing bit by bit to a vanishing point:
Dwindle 含有一点一点减少直到消失的意思
Their savings dwindled away. 他们的积蓄一点点地消耗殆尽了。
Lessen 1.v.tr.（及物动词）To make less; reduce.使变小；使减少 Use your seat belt to lessen the danger of injury in an accident.系上座椅安全带，减少交通事故中受伤的危险。(宾语为抽象名词) e.g. to lessen hazard, to lessen anxiety
2.v.intr. （不及物动词）To become less; decrease
His appetite lessens as his illness progresses. 随着病情的加重，他的食欲下降了。(主语为抽象名词)
Reduce : （及物动词）To bring down, as in extent, amount, or degree; e.g.1.They've reduced the prices in the shop, so it's a good time to buy.商店已经降低了商品的价格，看来现在是买东西的好时候。
2. The fire reduced the forest to a few trees.
Reduce emphasizes bringing down, as in size, degree, or intensity: Reduce 强调在大小、程度或强度方面下降或减少：
The workers reduced their wage demands.
工人们降低了他们在工资方面的要求。