Polish Notation Infix expression Infix notation is the notation commonly used in arithmetical and logical formulae and statements. It is characterized by the placement of operators between operands—"infixed operators"—such as the plus sign in 2 + 2. Convert Postfix expression Postfix notation is a mathematical notation. It is a way to write down equations and other mathematical formulae. Postfix notation is also known as Reverse Polish Notation Prefix Expression Prefix notation is a mathematical notation. It is a way to write down equations and other mathematical formulae. Prefix notation is also known as Polish notation. Stack Results for Postfix No Symbol Stack Expression 1 Symbol Stack Expression 1 Symbol Stack Expression