A priori knowledge is propositional knowledge that can be had without experience. It is usually contrasted with a posteriori knowledge, which requires experience. Mathematics and logic are usually considered a priori disciplines. The natural and social sciences are usually considered a posteriori disciplines.
... swedish author, winner of the Nobel Prize in literature
May 11 - Salvador Dalí, artist
May 17 - Jean Gabin[?], actor (+ 1976)
May 21 - Fats Waller, pianist (+ ...