pion vs pi-meson

pion and pi-meson both are nouns.

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

As nouns, pion and pi-meson are synonyms defined as:

pion and pi-meson: a meson involved in holding the nucleus together; produced as the result of high-energy particle collision

pion (noun)	pi-meson (noun)
a meson involved in holding the nucleus together; produced as the result of high-energy particle collision	a meson involved in holding the nucleus together; produced as the result of high-energy particle collision