ritual vs custom

ritual and custom both are nouns.

Word	Noun	Adjective	Verb	Adverb
ritual	Yes	Yes	No	No
custom	Yes	Yes	No	No

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

Other hypernyms of ritual include usage, usance.

ritual (noun)	custom (noun)
any customary observance or practice	accepted or habitual practice
the prescribed procedure for conducting religious ceremonies	habitual patronage
stereotyped behavior	a specific practice of long standing
	money collected under a tariff

ritual (adjective)	custom (adjective)
of or relating to or employed in social rites or rituals	made according to the specifications of an individual
of or relating to or characteristic of religious rituals