A person who directs an orchestra, choir, or ensemble.

• The leader guiding tempo, balance, and interpretation.

A public-transport worker who checks tickets and assists passengers.

• Common on trains, trams, and some buses.

A material or object that readily transmits electricity, heat, or sound.

• Opposite of an insulator.

One who leads, guides, or directs.

• A person acting as a guide or director.

In ring theory, an ideal measuring failure of integral closure.

• Especially the conductor of an order into its integral closure.

A grooved director used to guide surgical instruments.

• For example, guiding lithotriptic forceps.