Infix can also mean infix notation, that is, the operators go inside. This is the `normal' way people do math: 5 + (4 * 6). There's also prefix, which is what LISP uses, and RPN/postfix, which HP's calculators and Forth use. With the ease of parsing, and lack of ()'s, it's a shame RPN hasn't become the standard. Maybe ISO should start working on it?