priority vs precedency

priority and precedency both are nouns.

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

As nouns, priority and precedency are synonyms defined as:

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

As nouns, priority and precedency are synonyms defined as:

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

Other synonyms of priority include precedence.

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