Polish notation (PN), also known as normal Polish notation (NPN), Lukasiewicz  notation, Warsaw notation, Polish prefix notation or simply prefix notation, is a form of notation for logic, arithmetic, and algebra. Its distinguishing feature is that it places operators to the left of their operands. If the arity of the operators is fixed, the result is a syntax lacking parentheses or other brackets that can still be parsed without ambiguity. The Polish logician Jan Lukasiewicz invented this notation in 1924 in order to simplify sentential logic.