# Why is Euler's number an uppercase "E" and not a lowercase "e"?

Why is Euler's number an uppercase "E" and not a lowercase "e"?

Isn't Euler's Number normally expressed with a lowercase "e"?

• All MM-defined symbols start with uppercase Sep 11 '12 at 6:37
• No need to downvote, guys. Sep 11 '12 at 6:39
• You can also typeset it with Esc + ee + Esc... Sep 11 '12 at 8:07
• ...or enter \[ExponentialE] directly. Sep 11 '12 at 8:40
• And note that the 'e' you obtain from Esc + ee + Esc or from \[ExponentialE] has a doubled stroke on its left, as do the corresponding symbols from \[ImaginaryI] and [\DifferentialD] -- akin to the "blackboard bold" font commonly used in typesetting mathematical documents (e.g., with LaTeX). Sep 12 '12 at 15:07

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 e, i, n, or even sin or pi for your own variables without conflicting with Mathematica's constants and functions.

• Closed? "We expect answers to be supported by facts, references, or specific expertise, but this question will likely solicit debate, arguments, polling, or extended discussion." you're joking, surely... :) Sep 11 '12 at 15:34
• I agree, your answer clearly involves a fact. Reopened the question. It seemed to be close to being reopened anyway. Sep 11 '12 at 19:20
• @SjoerdC.deVries Thanks, I wouldn't have bothered, but this was the first question I've been able to answer for ages :) Sep 11 '12 at 19:33
• Just to explain my vote, I saw this from the review page which does not show the answers. So only the question, which was not really a serious/useful one, was shown with 4 close votes already. Also, the comments seemed to have explained it well, so I cast the final vote. Probably wouldn't have voted had I seen your answer, but someone else would've cast the final one :)
– rm -rf
Sep 11 '12 at 21:46
• @R.M No worries - I'm just being curmudgeonly today... It wasn't much of a question, true, but then it's no worse than this one :) Sep 11 '12 at 22:25