container ship vs containership

container ship and containership both are nouns.

Word	Noun	Adjective	Verb	Adverb
container ship	Yes	No	No	No
containership	Yes	No	No	No

As nouns, container ship and containership are synonyms defined as:

container ship and containership: a cargo ship designed to hold containerized cargoes

Other synonyms of container ship include container vessel.

container ship (noun)	containership (noun)
a cargo ship designed to hold containerized cargoes	a cargo ship designed to hold containerized cargoes