# 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"?

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All MM-defined symbols start with uppercase –  belisarius Sep 11 '12 at 6:37
No need to downvote, guys. –  belisarius Sep 11 '12 at 6:39
You can also typeset it with Esc + ee + Esc... –  Yves Klett Sep 11 '12 at 8:07
...or enter \[ExponentialE] directly. –  Ｊ. Ｍ. 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). –  murray Sep 12 '12 at 15:07

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.