persistent vs relentless

persistent and relentless both are adjectives.

Word	Noun	Adjective	Verb	Adverb
persistent	No	Yes	No	No
relentless	No	Yes	No	No

As adjectives, persistent and relentless are synonyms defined as:

Other synonyms of persistent include unrelenting.

persistent (adjective)	relentless (adjective)
retained; not shed	never-ceasing
never-ceasing	not to be placated or appeased or moved by entreaty
stubbornly unyielding
continually recurring to the mind