pardner vs cooperator

pardner and cooperator both are nouns.

Word	Noun	Adjective	Verb	Adverb
pardner	Yes	No	No	No
cooperator	Yes	No	No	No

As nouns, pardner and cooperator are synonyms defined as:

pardner and cooperator: an associate in an activity or endeavor or sphere of common interest

Other synonyms of pardner include collaborator, partner.

pardner (noun)	cooperator (noun)
an associate in an activity or endeavor or sphere of common interest	an associate in an activity or endeavor or sphere of common interest