prayer vs plea

prayer and plea both are nouns.

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

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

prayer (noun)	plea (noun)
the act of communicating with a deity (especially as a petition or in adoration or contrition or thanksgiving)	an answer indicating why a suit should be dismissed
earnest or urgent request	a humble request for help from someone in authority
a fixed text used in praying	(law) a defendant's answer by a factual matter (as distinguished from a demurrer)
reverent petition to a deity
someone who prays to God