Diode
(1) a two-terminal device that permits the flow of electric current in only one direction. Diodes are most often constructed by abutting n-type and p-type regions of a semiconductor, that has significantly higher electrical conductivity in one direction (forwardbiased) than the other (reverse-biased). Diode devices may be specially designed for low-power, high switching speed applications (signal diodes) or higher-power applications (rectifier diodes).
(2) a two terminal device that conducts in only one direction.