bunk vs couchette

bunk and couchette both are nouns.

Word	Noun	Adjective	Verb	Adverb
bunk	Yes	No	Yes	No
couchette	Yes	No	No	No

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

Other hyponyms of bunk include lower, lower berth, upper, upper berth.

bunk (noun)	couchette (noun)
a bed on a ship or train; usually in tiers	a compartment on a European passenger train; contains 4 to 6 berths for sleeping
a rough bed (as at a campsite)	a sleeping berth in a couchette compartment.
beds built one above the other
a long trough for feeding cattle
unacceptable behavior (especially ludicrously false statements)
a message that seems to convey no meaning

bunk (verb)	couchette (verb)
flee; take to one's heels; cut and run
provide with a bunk
avoid paying