AC adapter

external, enclosed power supply that converts mains electricity for an appliance

An AC adapter (hereafter called adapter) is a type of external power supply. It is often in a small case similar to the end of an electrical extension cord that plugs into an electrical wall outlet. Charger and power adapter are more common names.

Adapters are used with electrical devices that need the voltage and power changed from the power available at the wall outlet. They are used to power electronic devices with or without batteries. By 2022, they frequently could both power a device and charge its battery at the same time through the same connection point. Some adapters with a limited voltage and cycle range can only be used in one country, but many newer ones can be used in most countries. Using devices that require adapters increases safety since the wall outlet power is transformed to a lower safer voltage.  Many adapters connect to the device by a small electrical cord with a USB-C connector at the adapter end and a connector that matches the device at the other.