precedence vs antecedency

precedence and antecedency both are nouns.

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

As nouns, precedence and antecedency are synonyms defined as:

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

precedence (noun)	antecedency (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