Yankee vs Yank

Yankee and Yank both are nouns.

Word	Noun	Adjective	Verb	Adverb
Yankee	Yes	Yes	No	No
Yank	Yes	No	No	No

As nouns, Yankee and Yank are synonyms defined as:

Other synonyms of Yankee include Yankee-Doodle.

As nouns, Yankee and Yank are synonyms defined as:

Yankee and Yank: an American who lives in the North (especially during the American Civil War)

Other synonyms of Yankee include Northerner.

Yankee (noun)	Yank (noun)
an American (especially to non-Americans)	an American (especially to non-Americans)
an American who lives in New England	an American who lives in the North (especially during the American Civil War)
an American who lives in the North (especially during the American Civil War)

Yankee (adjective)	Yank (adjective)
used by Southerners for an inhabitant of a northern state in the United States (especially a Union soldier)