petitioner vs postulant

petitioner and postulant both are nouns.

Word	Noun	Adjective	Verb	Adverb
petitioner	Yes	No	No	No
postulant	Yes	No	No	No

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

petitioner: one praying humbly for something
postulant: one submitting a request or application especially one seeking admission into a religious order

Other hyponyms of petitioner include besieger, canvasser, solicitor.

petitioner (noun)	postulant (noun)
one praying humbly for something	one submitting a request or application especially one seeking admission into a religious order
someone who petitions a court for redress of a grievance or recovery of a right