trench vs encroach

trench is a noun but encroach is not a noun.

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

As verbs, trench and encroach are synonyms defined as:

Other synonyms of trench include entrench, impinge.

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

trench (verb)	encroach (verb)
cut or carve deeply into	advance beyond the usual limit
dig a trench or trenches	impinge or infringe upon
cut a trench in, as for drainage
fortify by surrounding with trenches
set, plant, or bury in a trench
impinge or infringe upon