pion vs meson

pion and meson both are nouns.

Word	Noun	Adjective	Verb	Adverb
pion	Yes	No	No	No
meson	Yes	No	No	No

As nouns, meson is a hypernym of pion; that is, meson is a word with a broader meaning than pion:

pion: a meson involved in holding the nucleus together; produced as the result of high-energy particle collision
meson: an elementary particle responsible for the forces in the atomic nucleus; a hadron with a baryon number of 0

Other hypernyms of pion include mesotron.

pion (noun)	meson (noun)
a meson involved in holding the nucleus together; produced as the result of high-energy particle collision	an elementary particle responsible for the forces in the atomic nucleus; a hadron with a baryon number of 0