flotation device vs life preserver

flotation device and life preserver both are nouns.

Word	Noun	Adjective	Verb	Adverb
flotation device	Yes	No	No	No
life preserver	Yes	No	No	No

As nouns, flotation device and life preserver are synonyms defined as:

flotation device and life preserver: rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning

Other synonyms of flotation device include preserver.

flotation device (noun)	life preserver (noun)
rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning	rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning