ditch vs sunk fence

ditch and sunk fence both are nouns.

Word	Noun	Adjective	Verb	Adverb
ditch	Yes	No	Yes	No
sunk fence	Yes	No	No	No

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

ditch: a long narrow excavation in the earth
sunk fence: a ditch with one side being a retaining wall; used to divide lands without defacing the landscape

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

ditch (noun)	sunk fence (noun)
a long narrow excavation in the earth	a ditch with one side being a retaining wall; used to divide lands without defacing the landscape
any small natural waterway

ditch (verb)	sunk fence (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