communication trench vs approach trench

communication trench and approach trench both are nouns.

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

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

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

communication trench (noun)	approach 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