DEPUTY

[noun] [C] - a person who is given the power to act instead of another person, or the person whose rank is immediately below that of the leader of an organizationI'd like you to meet Ann Gregory, my deputy.I'm acting as deputy while the boss is away.She's the deputy (head) of a large school in the East End of London.He is the deputy chairperson/Foreign Minister/manager/mayor/(US) sheriff.