One who conducts or leads; a guide; a director.

(music) A person who conducts an orchestra, choir or other music ensemble; a professional whose occupation is conducting.

(rail transport) A person who takes tickets on public transportation and also helps passengers.

(physics) Something that can transmit electricity, heat, light, or sound.

(mathematics) An ideal of a ring that measures how far it is from being integrally closed

A grooved sound or staff used for directing instruments, such as lithontriptic forceps; a director.

(architecture) A leader.