mother board vs circuit board

mother board and circuit board both are nouns.

Word	Noun	Adjective	Verb	Adverb
mother board	Yes	No	No	No
circuit board	Yes	No	No	No

As nouns, circuit board is a hypernym of mother board; that is, circuit board is a word with a broader meaning than mother board:

mother board: the main circuit board for a computer
circuit board: a printed circuit that can be inserted into expansion slots in a computer to increase the computer's capabilities

Other hypernyms of mother board include add-in, board, card, circuit card, plug-in.

mother board (noun)	circuit board (noun)
the main circuit board for a computer	a printed circuit that can be inserted into expansion slots in a computer to increase the computer's capabilities