The phrase "key person" refers to an individual who holds a critical role in an organization or a group. This person is often responsible for making important decisions and implementing strategies to achieve the group's goals. Synonyms for the phrase include "crucial figure," "central player," "vital member," and "principal actor." Other phrases that convey a similar meaning include "linchpin," "cornerstone," "nucleus," "lynchpin," and "mainstay." These words and phrases highlight the importance of an individual's contribution to the success of a team or organization. Whether it's in business, politics, or social pursuits, a key person plays a vital role in achieving shared objectives.