# Why is $e$ the Identity?

Some authors use $e$ to be the identity element of a group instead of $1$. What is the origin of this notation? Was this before or after we used $e$ to represent the base of the natural logarithm? If after, is there some connection?

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mathoverflow.net/questions/87794/… –  user61527 Feb 8 '14 at 21:33

## 1 Answer

We germans (or Kraut, as you might call us) call the identity element "Einheitselement", and hence denote it by $e$ (even though of course not every one does). Similarily it is common to denote a field by $k$ for "Körper"; anyway a great deal of mathematical terminology is of german origin. Likewise the french often denote vector spaces by $E$ ("espace").

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Ich danke Ihnen. –  Joe Johnson 126 Feb 8 '14 at 21:56
kraut XD sehr gut –  qwr Feb 8 '14 at 22:44
War mir ein Verrrgnügen –  user88576 Feb 8 '14 at 23:05
Ah, Germany, the country of coal, blood, and beer (your flag). (Idiots forgot beer the last two times. Can't have Germany without beer.) –  columbus8myhw Dec 7 '14 at 2:56