That’s it. No matter what app you’re in or font you’re using, the Pi symbol will appear in the place of the letter “P” when you hold down the option key. Then, when you want to type the Pi symbol, ...
Whether you have just switched from a PC to a Mac and have discovered that the ” and @ keys aren’t where you were expecting, you can’t find the euro sign, pound sign, or hash key on your Mac keyboard, ...