How Do You Write Postscript?

How Do You Write Postscript? Add more postscripts by adding a ‘P’ to “P.S.” The “post” in “postscript” is a Latin word meaning ‘after’ (“script” means ‘writing’ in Latin), and so when you add another ‘P’ to a “P.S.’”, you are creating an “after-after-writing” to form P.P.S. What is the correct way to write PS?