pedant

pedant \PED-nt\, noun:

a person who makes a show of detailed knowledge, esp. relying on books; also, a narrow-minded teacher or scholar

All too often, science fiction provokes the pedant in professional scientists, for whom a beautiful story can be ruined by a single petty error.
-- Jerry A. Coyne, The Truth Is Way Out There, New York Times, October 10, 1999

Yet Eyton is no little pedant; he confesses frankly that for a boy of 9 he does not know much Greek, though his Latin is adequate.
-- Robertson Davies, Speaking Of Books, New York Times, February 14, 1962

c 1586, "schoolmaster," from Middle French pédant, from Italian pedante "teacher, schoolmaster," apparently an alteration of Late Latin paedagogantem, from paedagogare. Meaning "person who trumpets minor points of learning" first recorded 1593.