priority vs antecedency

priority and antecedency both are nouns.

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

As nouns, priority and antecedency are synonyms defined as:

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

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