Holy Communion vs ritual

Holy Communion and ritual both are nouns.

Word	Noun	Adjective	Verb	Adverb
Holy Communion	Yes	No	No	No
ritual	Yes	Yes	No	No

As nouns, ritual is a hypernym of Holy Communion; that is, ritual is a word with a broader meaning than Holy Communion:

Holy Communion: the act of participating in the celebration of the Eucharist
ritual: the prescribed procedure for conducting religious ceremonies

Holy Communion (noun)	ritual (noun)
the act of participating in the celebration of the Eucharist	any customary observance or practice
	the prescribed procedure for conducting religious ceremonies
	stereotyped behavior

Holy Communion (adjective)	ritual (adjective)
	of or relating to or employed in social rites or rituals
	of or relating to or characteristic of religious rituals