Explanation: When selecting a junction diode for most applications, the two most critical specifications are its ability to handle current in the forward direction and voltage in the reverse direction. **Maximum forward current** indicates the maximum amount of current the diode can safely conduct when it is forward-biased (switched "on") without overheating and being destroyed. Exceeding this limit will cause thermal runaway and failure. **PIV (Peak Inverse Voltage)**, also known as repetitive peak reverse voltage (VRRM), specifies the maximum instantaneous reverse-bias voltage that can be applied across the diode without causing it to break down and conduct in the reverse direction. This is crucial in rectifier circuits, where diodes are constantly subjected to reverse voltages when the AC cycle reverses. While other specifications like capacitance (important for high-frequency circuits) or reverse leakage current (usually very small and often negligible) exist, maximum forward current and PIV are the primary considerations for ensuring a diode operates reliably in the vast majority of power supply, switching, and rectifier applications.