crosspiece vs transom

crosspiece and transom both are nouns.

Word	Noun	Adjective	Verb	Adverb
crosspiece	Yes	No	No	No
transom	Yes	No	No	No

As nouns, transom is a hyponym of crosspiece; that is, transom is a word with a more specific, narrower meaning than crosspiece:

crosspiece: a transverse brace
transom: a horizontal crosspiece across a window or separating a door from a window over it

Other hyponyms of crosspiece include crossbar, rundle, rung, spoke, round, rung, stave, cross thwart, thwart, traverse.

crosspiece (noun)	transom (noun)
a transverse brace	a horizontal crosspiece across a window or separating a door from a window over it
a horizontal beam that extends across something	a window above a door that is usually hinged to a horizontal crosspiece over the door