approach trench vs communication trench

approach trench and communication trench both are nouns.

Word	Noun	Adjective	Verb	Adverb
approach trench	Yes	No	No	No
communication trench	Yes	No	No	No

As nouns, approach trench and communication trench are synonyms defined as:

approach trench and communication trench: a trench that provides protected passage between the rear and front lines of a defensive position

approach trench (noun)	communication trench (noun)
a trench that provides protected passage between the rear and front lines of a defensive position	a trench that provides protected passage between the rear and front lines of a defensive position