antecedency vs priority

antecedency and priority both are nouns.

Word	Noun	Adjective	Verb	Adverb
antecedency	Yes	No	No	No
priority	Yes	No	No	No

As nouns, antecedency and priority are synonyms defined as:

Other synonyms of antecedency include antecedence, anteriority, precedence, precedency.

antecedency (noun)	priority (noun)
preceding in time	preceding in time
	status established in order of importance or urgency