chest vs pyx

chest and pyx both are nouns.

Word	Noun	Adjective	Verb	Adverb
chest	Yes	No	No	No
pyx	Yes	No	No	No

As nouns, pyx is a hyponym of chest; that is, pyx is a word with a more specific, narrower meaning than chest:

chest (noun)	pyx (noun)
box with a lid; used for storage; usually large and sturdy	any receptacle in which wafers for the Eucharist are kept
furniture with drawers for keeping clothes	a chest in which coins from the mint are held to await assay
the part of the human torso between the neck and the diaphragm or the corresponding part in other vertebrates
the front of the trunk from the neck to the abdomen