Operative
Part of speech: noun
Definition: An employee or other worker with some particular function or skill. A spy, secret agent, or detective.
Part of speech: adjective
Definition: Effectual or important. Functional, in working order.
Significant
Part of speech: adjective
Definition: Signifying something; carrying meaning.Having a covert or hidden meaningHaving a noticeable or major effect; notableReasonably large in number or amountHaving a low probability of occurring by chance (for example, having high correlation and thus likely to be related).
Example sentence: Literature is one of the most interesting and significant expressions of humanity.