precedency vs priority

precedency and priority both are nouns.

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

As nouns, precedency and priority are synonyms defined as:

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

As nouns, precedency and priority are synonyms defined as:

precedency and priority: status established in order of importance or urgency

Other synonyms of precedency include precedence.

precedency (noun)	priority (noun)
the act of preceding in time or order or rank (as in a ceremony)	preceding in time
preceding in time	status established in order of importance or urgency
status established in order of importance or urgency