preserver vs life vest

preserver and life vest both are nouns.

Word	Noun	Adjective	Verb	Adverb
preserver	Yes	No	No	No
life vest	Yes	No	No	No

As nouns, life vest is a hyponym of preserver; that is, life vest is a word with a more specific, narrower meaning than preserver:

preserver: rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning
life vest: life preserver consisting of a sleeveless jacket of buoyant or inflatable design

Other hyponyms of preserver include life belt, life buoy, life ring, lifesaver, cork jacket, life jacket, water wings.

preserver (noun)	life vest (noun)
rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning	life preserver consisting of a sleeveless jacket of buoyant or inflatable design
a skilled worker who is employed to restore or refinish buildings or antique furniture
someone who keeps safe from harm or danger
a cook who preserves fruits or meat