What electronic component allows current to flow in only one direction?

A diode is a semiconductor device designed to act like a one-way check valve for electrical current. It allows current to pass easily in one direction (when forward-biased) but strongly blocks it in the reverse direction (when reverse-biased). This one-way property is essential for tasks like rectification, which is the process of converting alternating current (AC) into direct current (DC) in power supplies. The other options do not share this directional property. A resistor limits current equally in both directions. A fuse simply breaks the circuit entirely if the current exceeds a safe limit, regardless of which way the current is flowing.