persistency vs tenacity

persistency and tenacity both are nouns.

Word	Noun	Adjective	Verb	Adverb
persistency	Yes	No	No	No
tenacity	Yes	No	No	No

As nouns, persistency and tenacity are synonyms defined as:

Other synonyms of persistency include doggedness, perseverance, persistence, pertinacity, tenaciousness.

persistency (noun)	tenacity (noun)
persistent determination	persistent determination