Zener diodes operate similarly to regular diodes in that they allow current flow in the forward direction, but they also allow it to flow in the reverse direction when its voltage exceeds what is known as the "breakdown voltage". Other terms for this electrical property are "zener knee voltage" zener voltage" and "avalanche point". Zeners are used in applications such as shunt regulators, wave-form clippers (when two are used), surge protectors and noise generators.