ditch vs trench

ditch and trench both are nouns.

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

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

ditch: a long narrow excavation in the earth
trench: a ditch dug as a fortification having a parapet of the excavated earth

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

As verbs, ditch and trench are synonyms defined as:

ditch (noun)	trench (noun)
a long narrow excavation in the earth	a ditch dug as a fortification having a parapet of the excavated earth
any small natural waterway	any long ditch cut in the ground
	a long steep-sided depression in the ocean floor

ditch (verb)	trench (verb)
crash or crash-land	cut or carve deeply into
cut a trench in, as for drainage	dig a trench or trenches
make an emergency landing on water	cut a trench in, as for drainage
forsake	fortify by surrounding with trenches
throw away	set, plant, or bury in a trench
sever all ties with, usually unceremoniously or irresponsibly	impinge or infringe upon