Miscellaneous operations: Standard mathematical operations like multiplication and division. Relations: Relational symbols like less than, greater than, not equals to, subest, etc.

Unicode is a massive, sprawling effort that pairs a number to every unique character in a language, every punctuation mark, every math symbol, and much more. And nearly all of it is available ...

The pi symbol isn't readily available on your iPhone's default keyboard, but there are tricks you can do to change that and have it available whenever you need.