1. 改进剂：impression cylinder 压印滚筒 | improver 改进剂 | improving agent 改进剂

2. 改进剂;实习生：improvement 改善 | improver 改进剂;实习生 | improvidence 无远见;不节约

3. 改进者：improver 改进物 | improver 改进者 | improver 练习生

noun

1. a component that is added to something to improve it

e.g. the addition of a bathroom was a major improvement
the addition of cinnamon improved the flavor

Synonym: additionadd-on

2. someone devoted to the promotion of human welfare and to social reforms

Synonym: humanitariando-gooder