or Rabbi Jonah born 990, Córdoba died 1050, Zaragoza, Spain Spanish scholar famed as a Hebrew grammarian and lexicographer. A practicing physician and a devout Jew, he founded the study of Hebrew syntax, establishing the rules of biblical exegesis and clarifying many difficult passages. His principal work was the two-volume Book of Exact Investigation, a Hebrew grammar and lexicon. All his writings were in Arabic, and he made extensive comparisons of Hebrew and Arabic words