The nuremberg laws identified a jew as someone who

Had Jewish ancestors. This was different from historic anti Semitism because it defined Jewishness as hereditary (race) rather than by practice (religion). Three categories of Jews were created: "Full Jews," who either practiced Judaism or had at least 3 Jewish grandparents, regardless of religious practice; "First Class Mischlinge" (Half Jewish), who had 2 Jewish grandparents, didn't practice Judaism, and didn't have a Jewish spouse; and "Second Class Mischlinge" (One Quarter Jewish) who had one Jewish grandparent and did not practice Judaism