(Or "Reverse Polish Notation", RPN) One of the possible orderings of functions and operands: in postfix notation the functions are preceded by all their operands. For example, what may normally be written as "1+2" becomes "1 2 +". Postfix notation is well suited for stack based architectures but modern compilers reduced this advantage considerably. The best-known language with postfix syntax is forth.

Compare: infix notation, prefix notation.