decline
v.
英文释义1：to gradually become less, worse, or lower
[Example] His interest in the project declined after his wife died.
英文释义2：to refuse
[Example] I invited him to the meeting but he declined.
decrease
v.
英文释义1：to become less, or to make something become less:
[Example] Total unemployment has decreased in the past year.
n.
英文释义1：a reduction
[Example] There has been a decrease in the number of visitors.
reduce
v.
英文释义1：to become or to make something become smaller in size, amount, degree, importance, etc.
[Example] The plane reduced speed as it approached the airport.
英文释义2：to heat a liquid until it becomes thicker and less in quantity
[Example] Reduce the sauce by boiling for five minutes.
