Infix notation

Infix notation is one of the 4 possible ways to describe a program. It is not as powerful as the others, so people usually add parenthesis, which makes it a combined notation (Infix-Surround).

Examples
Here is an example of pure infix: 1 + 2 And a way to encode * + 2 2 4 in infix-surround: (2 + 2) * 4