Mother board and Plug-in

Mother board noun - The main circuit board for a computer.

Plug-in and mother board are semantically related. In some cases you can use "Plug-in" instead a noun phrase "Mother board".

Plug-in noun - A printed circuit that can be inserted into expansion slots in a computer to increase the computer's capabilities.

Mother board and plug-in are semantically related. Sometimes you can replace phrase "Mother board" with "Plug-in", this phrases are similar.