operative
adj. 运转正常的，有效的；手术的；（词）最重要的，关键的
n. 技工，工人；密探，（尤指政府的）特工人员
复数 operatives
例句
This law becomes operative immediately.
本法规即时生效。
《牛津词典》
The station will be fully operative again in January.
该站将于一月份全部恢复运营。
I was in love with her—'was' being the operative word.
在I was in love with her这句话中，was是关键词。
