kettle vs boiler

kettle and boiler both are nouns.

Word	Noun	Adjective	Verb	Adverb
kettle	Yes	No	No	No
boiler	Yes	No	No	No

As nouns, kettle and boiler are synonyms defined as:

kettle and boiler: a metal pot for stewing or boiling; usually has a lid

kettle (noun)	boiler (noun)
a metal pot for stewing or boiling; usually has a lid	sealed vessel where water is converted to steam
a large hemispherical brass or copper percussion instrument with a drumhead that can be tuned by adjusting the tension on it	a metal pot for stewing or boiling; usually has a lid
(geology) a hollow (typically filled by a lake) that results from the melting of a mass of ice trapped in glacial deposits
the quantity a kettle will hold