tenaciousness vs persistency

tenaciousness and persistency both are nouns.

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

As nouns, tenaciousness and persistency are synonyms defined as:

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

tenaciousness (noun)	persistency (noun)
persistent determination	persistent determination