Definition - What does Ethernet Adapter mean?
An Ethernet adapter is a piece of hardware that allows a device or workstation to access an Ethernet connection. Ethernet adapters can be add-ons that go into an expansion board, or they can be directly installed in the motherboard of a computer or device.
Techopedia explains Ethernet Adapter
The most common kind of Ethernet adapter is a PC card, which has an Ethernet connection and a circuit board. Some versions of these adapters can be simply fitted into a corresponding hole in the plastic tower of a desktop computer. Ethernet adapters can use various kinds of Cat5 or Cat6 cables to hook up to an Ethernet connection.
As more local networks started to use wireless systems, the Ethernet adapter started to lose ground to network adapter cards that fit into various devices to allow wireless connections. An Ethernet adapter is still instrumental in affecting physical cabled hookups, but many users choose to use a wireless router and wireless adapters for individual devices.