prayer vs Agnus Dei

prayer and Agnus Dei both are nouns.

Word	Noun	Adjective	Verb	Adverb
prayer	Yes	No	No	No
Agnus Dei	Yes	No	No	No

As nouns, Agnus Dei is a hyponym of prayer; that is, Agnus Dei is a word with a more specific, narrower meaning than prayer:

Other hyponyms of prayer include Mass, Shema.

prayer (noun)	Agnus Dei (noun)
the act of communicating with a deity (especially as a petition or in adoration or contrition or thanksgiving)	figure of a lamb; emblematic of Christ
earnest or urgent request	a liturgical prayer beginning with these Latin words
a fixed text used in praying
reverent petition to a deity
someone who prays to God