eccentric vs screwball

eccentric and screwball both are nouns.

Word	Noun	Adjective	Verb	Adverb
eccentric	Yes	Yes	No	No
screwball	Yes	Yes	No	No

As nouns, screwball is a hyponym of eccentric; that is, screwball is a word with a more specific, narrower meaning than eccentric:

Other hyponyms of eccentric include crackpot, crank, fruitcake, nut, nut case, nutter, wacko, whacko.

eccentric (noun)	screwball (noun)
a person with an unusual or odd personality	a pitch with reverse spin that curves toward the side of the plate from which it was thrown
a person of a specified kind (usually with many eccentricities)	a whimsically eccentric person

eccentric (adjective)	screwball (adjective)
not having a common center; not concentric	foolish; totally unsound
conspicuously or grossly unconventional or unusual