prayer vs requiescat

prayer and requiescat both are nouns.

Word	Noun	Adjective	Verb	Adverb
prayer	Yes	No	No	No
requiescat	Yes	No	No	No

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

prayer (noun)	requiescat (noun)
the act of communicating with a deity (especially as a petition or in adoration or contrition or thanksgiving)	a prayer for the repose of the soul of a dead person
earnest or urgent request
a fixed text used in praying
reverent petition to a deity
someone who prays to God