ceaselessness vs incessancy

ceaselessness and incessancy both are nouns.

Word	Noun	Adjective	Verb	Adverb
ceaselessness	Yes	No	No	No
incessancy	Yes	No	No	No

As nouns, ceaselessness and incessancy are synonyms defined as:

ceaselessness and incessancy: the quality of something that continues without end or interruption

Other synonyms of ceaselessness include continuousness, incessantness.

ceaselessness (noun)	incessancy (noun)
the quality of something that continues without end or interruption	the quality of something that continues without end or interruption