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.