ditch vs drainage ditch

ditch and drainage ditch both are nouns.

Word	Noun	Adjective	Verb	Adverb
ditch	Yes	No	Yes	No
drainage ditch	Yes	No	No	No

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

Other hyponyms of ditch include irrigation ditch, ha-ha, haw-haw, sunk fence, trench, trench.

ditch (noun)	drainage ditch (noun)
a long narrow excavation in the earth	a ditch for carrying off excess water or sewage
any small natural waterway

ditch (verb)	drainage ditch (verb)
crash or crash-land
cut a trench in, as for drainage
make an emergency landing on water
forsake
throw away
sever all ties with, usually unceremoniously or irresponsibly