tanker vs tank ship

tanker and tank ship both are nouns.

Word	Noun	Adjective	Verb	Adverb
tanker	Yes	No	No	No
tank ship	Yes	No	No	No

As nouns, tanker and tank ship are synonyms defined as:

Other synonyms of tanker include oil tanker, oiler.

tanker (noun)	tank ship (noun)
a cargo ship designed to carry crude oil in bulk	a cargo ship designed to carry crude oil in bulk
a motor vehicle designed to carry liquefied loads, dry bulk cargo or gases on roads.
a soldier who drives a tank