# My Prefix is Polish

My prefix is Polish
My postfix, just the opposite
My infix is easier to read
I can be anything you choose, but never, ever will I be a Tion.

What am I?

This figures out to be

notation

My prefix is Polish

Polish notation, aka prefix notation.

My postfix, just the opposite

Postfix notation is also called Reverse Polish Notation.

My infix is easier to read

Infix notation is easier to read for humans.

I can be anything you choose, but never, ever will I be a Tion.

You can select you own notation, but this is not a tion.

• I wanted to invert the whole thing, so please don't do that with the 4th spoiler block :-) (You are correct, of course) – Bass Jan 21 at 23:48
• Oops, fixed that. Maybe a T ion is ${^3}{H^+}$. – Tom Jan 22 at 0:01
• Oo, brilliant! Editing the question :-) (no cancel that, too contrived.) – Bass Jan 22 at 0:06
• (It's a brilliant clue, but since the whole point is pretending to not be brilliant, it would probably defeat the purpose) – Bass Jan 22 at 0:15