antecedency vs precedency

antecedency and precedency both are nouns.

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

As nouns, antecedency and precedency are synonyms defined as:

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

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