donjon vs castle

donjon and castle both are nouns.

Word	Noun	Adjective	Verb	Adverb
donjon	Yes	No	No	No
castle	Yes	No	Yes	No

donjon (noun)	castle (noun)
the main tower within the walls of a medieval castle or fortress	interchanging the positions of the king and a rook
	a large building formerly occupied by a ruler and fortified against attack
	(chess) the piece that can move any number of unoccupied squares in a direction parallel to the sides of the chessboard
	a large and stately mansion

donjon (verb)	castle (verb)
	move the king two squares toward a rook and in the same move the rook to the square next past the king