offering vs offertory

offering and offertory both are nouns.

Word	Noun	Adjective	Verb	Adverb
offering	Yes	No	No	No
offertory	Yes	No	No	No

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

offering: money contributed to a religious organization; item or items contributed to a religious organization for religious purposes
offertory: the offerings of the congregation at a religious service

Other hyponyms of offering include tithe, hearth money, Peter's pence, thank offering.

offering (noun)	offertory (noun)
the act of contributing to the funds of a church or charity	the offerings of the congregation at a religious service
something offered (as a proposal or bid)
the verbal act of offering
money contributed to a religious organization; item or items contributed to a religious organization for religious purposes