diode – a component that allows current to flow in one direction

(pronounced dy-ohd)

To remember the meaning of diode, use the following mnemonic:

The diet the toad (diode) was on only allowed it to eat currants (current) that flowed in one direction.

A diode is an electrical component that allows electric current to flow through it in only one direction, acting like a one-way valve for electricity. It has two ends called terminals: the anode (positive end) and the cathode (negative end). 

When the diode is connected in forward bias, meaning the anode is connected to the positive side of a power supply and the cathode to the negative side, current flows through it easily. However, when it is connected in reverse bias (the opposite way around), the diode blocks the current and prevents it from flowing. This property makes diodes extremely useful in electronic circuits for tasks such as converting alternating current (AC) to direct current (DC), protecting circuits from damage if batteries are inserted the wrong way, and controlling the direction of current flow. 

A common type of diode is the light-emitting-diode (LED), which emits light when current flows through it in the forward direction.