seaplane vs airplane

seaplane and airplane both are nouns.

Word	Noun	Adjective	Verb	Adverb
seaplane	Yes	No	Yes	No
airplane	Yes	No	No	No

As nouns, airplane is a hypernym of seaplane; that is, airplane is a word with a broader meaning than seaplane:

seaplane: an airplane that can land on or take off from water
airplane: an aircraft that has a fixed wing and is powered by propellers or jets

Other hypernyms of seaplane include aeroplane, plane.

seaplane (noun)	airplane (noun)
an airplane that can land on or take off from water	an aircraft that has a fixed wing and is powered by propellers or jets

seaplane (verb)	airplane (verb)
glide on the water in a hydroplane