pyxis vs pyxidium

pyxis and pyxidium both are nouns.

Word	Noun	Adjective	Verb	Adverb
pyxis	Yes	No	No	No
pyxidium	Yes	No	No	No

As nouns, pyxis and pyxidium are synonyms defined as:

pyxis and pyxidium: fruit of such plants as the plantain; a capsule whose upper part falls off when the seeds are released

pyxis (noun)	pyxidium (noun)
a small box used by ancient Greeks to hold medicines	fruit of such plants as the plantain; a capsule whose upper part falls off when the seeds are released
fruit of such plants as the plantain; a capsule whose upper part falls off when the seeds are released