encroach vs trench

encroach is not a noun while trench is a noun.

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

As verbs, encroach and trench are synonyms defined as:

Other synonyms of encroach include entrench, impinge.

encroach (noun)	trench (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

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