# Why exactly was $\epsilon$ chosen to denote a very small quantity? [closed]

I tried to search the defintion of $\epsilon$, but only got that it is the fifth letter in the Greek alphabet.

I want to know why it was chosen the way it was?

This is something not very obvious, unlike the symbol $\in$, which means element of. That makes sense because $\in$ looks like an $E$ which can stand for element.

But epsilon is just an alphabet letter, and so why was it chosen?

## closed as off-topic by Jack, Namaste, Daniel W. Farlow, Claude Leibovici, user223391 Jul 18 '17 at 20:56

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• I think that $\epsilon$ and $\delta$ were chosen because they're consecutive letters in the Greek alphabet. – Omnomnomnom Jul 2 '17 at 23:31
• I think $\delta$ was chosen because it sounds like the "d" in difference. Also the upper case, $\Delta$ was being used to indicate a small change in a quantity. After that, $\epsilon$ was chosen because it is the next Greek letter after $\delta$. – steven gregory Jul 2 '17 at 23:35
• Possible duplicate of math.stackexchange.com/questions/530792/… – Dhruv Kohli - expiTTp1z0 Jul 2 '17 at 23:45
• See the post: Who gave you the epsilon ?: Cauchy in his 1823 textbook used trhe Greek letters $\alpha, \beta, \gamma, \delta, \epsilon, \ldots$ for "nombres très-petites" (very small numbers). In the first chapter he started using $\alpha$ and $\beta$ and in the proof of the Theorem (7th Lecture) he introduced $\delta$ and $\epsilon$. Thus, I think that there is no special "allusion" behind the choice of them. – Mauro ALLEGRANZA Jul 3 '17 at 6:17
• mathoverflow.net/questions/82302/… – Hans Lundmark Jul 3 '17 at 6:22