Is ancient and door a noun?

The Word 'ancient' is both an adjective and a noun. The noun ancient is a singular, common, abstract noun; a Word for an aged person; the plural form is a Word for the civilized peoples of ancient times and especially of Greece and Rome.

The Word 'door' is a noun, a singular, common, concrete noun. The noun door is a Word for a hinged, sliding, or revolving barrier at the entrance to a building, room, or vehicle; a portal.