maven \MEY-vn\ (noun) - An expert or connoisseur; someone with profound knowledge of a subject.
"Hesh was the local maven of 60's era music, with an extensive record library and reference books."
Yiddish "meyvn" from Hebrew meebin "expert," active participle of heebin "to understand," derived stem of the radical bn "discern, understand." "Maven" is a lexical orphan without an adjective or verb to accompany it. The Hebrew plural, "mavinim," is used only facetiously. The spelling "mavin" has alternated with the current spelling over the past century but most dictionaries have now settled on the spelling we use above.