1、decrease
vi. become smaller or fewer in size, amount, intensity or degree
减少，减小，减弱，降低
vt. make smaller or fewer in size, amount, intensity or degree
使减小，使减少
n. an instance or example of becoming smaller or fewer
减小或减少
2、fall
vi. decrease in number, amount, intensity or quality
减少，下降
In 1987 imports into Britain fell by 12 per cent.
1987年，英国进口降低了12%。
3、reduce
vt. make smaller or less in amount, degree, or size
减少（数量），降低（程度），缩小（规模）
the need for businesses to reduce costs
公司降低成本的需要
vi. become smaller or less in size, amount, or degree
（规模）缩小，（数量）减少，（程度）降低
the number of priority homeless cases has reduced slightly
被优先照顾的无家可归者人数已微幅下降
4、down
to or at a lower price, value or rank
（价格、价值或等级）由高到低
output was down by 20 per cent
产量下降了20%
5、drop
v. make or become lower, weaker or less
（使）降低，（使）变弱，（使）减少
pre-tax profits dropped by 37 per cent
税前利润减少了37%
n. a fall in amount, quality or rate
（数量、质量、比率的）减少，降低
a significant drop in consumer spending
消费者开支的显著减少
壬生京三郎
