Why is Euler's number an uppercase "E" and not a lowercase "e"?
Isn't Euler's Number normally expressed with a lowercase "e"?
As often happens here, the comment provides the answer, but here's the answer from Stephen Wolfram's book about Mathematica (the second edition of "Mathematica, a System for Doing Mathematics by Computer" which I bought for £0.01 on Amazon):
Mathematica uses both upper- and lower-case letters. There is a convention that built-in Mathematica objects always have names starting with upper-case (capital) letters. To avoid confusion, you should always choose names for your own variables that start with lower-case letters.
This means that you can use
n, or even
pi for your own variables without conflicting with Mathematica's constants and functions.