Order vs priest

Order and priest both are nouns.

Word	Noun	Adjective	Verb	Adverb
Order	Yes	No	No	No
priest	Yes	No	No	No

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

Order: (usually plural) the status or rank or office of a Christian clergyman in an ecclesiastical hierarchy
priest: a clergyman in Christian churches who has the authority to perform or administer various religious rites; one of the Holy Orders

Other hyponyms of Order include acolyte, anagnost, deacon, doorkeeper, ostiarius, ostiary, exorcist, lector, reader, subdeacon.

Order (noun)	priest (noun)
(usually plural) the status or rank or office of a Christian clergyman in an ecclesiastical hierarchy	a clergyman in Christian churches who has the authority to perform or administer various religious rites; one of the Holy Orders
	a person who performs religious duties and ceremonies in a non-Christian religion