It depends from region, in math there is no SI so there are no fixed symbols. For example my math teacher traveled around the world and she says that she has seen 3 different ways calculating determinants (different in Europe, India and the Arab worlds), in some countries the definite integral boundaries are switched, and since combinatorics is a relatively new branch markings differ from school to school.
We always used the reversed 3
Firstly the style of a symbol is even less important than the symbol. But then perhaps while there are traditional symbols for particular purposes (Eg epsilon-delta], there are probably traditional styles as well.
Apparently, there is even a word for the distinction. The version that does not look like a reversed 3 (i.e. the one I called "Euro-style") is called "lunate". And the Euro symbol was indeed inspired by the lunate epsilon.
I think only of the curly epsilon in calculus, but had an idea that the Euro-style epsilon might be more popular in set theory. But wikipedia's article on epsilon numbers and on ordinal numbers only uses curly epsilons. I may have been subconsciously thinking of the resemblance between the set membership symbol and the lunate epsilon (apparently, there is no connection between the two except they look similar).
Actually mf92, if there is one science where you'd expect a clear agreement on notations (SI if you will), it would be mathematics. There are of course several other examples where styles differ, but I think that is different. For example I usually write probabilities and expected values with \mathbb{P} and \mathbb{E}-styles, while others write simply P(..), or Pr(..). But we do not refer to the symbols \mathbb{P}, P or Pr by the same name, but only use them for the same meaning.
That's why this one bothers me most, because both actually refer to the same symbol, namely the Greek epsilon. I mean, if I started writing the "small B" as "a", I'm sure that would be confusing as well. So why should one symbol have two different ways of writing it? And as far as I can tell, there was no such ambiguity until mathematics decided to use two notations, so the ambiguity was even created at some point.
Anyway it just surprises me that apparently this confusion was created, rather than that it already existed. The Greek small epsilon is the one with a curly back, and imo some incompetent mathematicians (using the wrong notation) forced an unnecessary split in the mathworld by using a wrong notation for the epsilon. Shame on them :/
Actually, I just checked some of my own stuff, and I see that standard LaTeX compilation actually gives the epsilons with straight backs... How ugly! :(
But coincidentally, the journal I'm submitting a paper to uses some times-like font (mathptmx-package) which uses curly epsilons. I don't really like the times-font, but I do like the curly epsilons. Well done, journal! :)
I've always used/been taught reversed 3 style for analysis proofs, and I've always used/been taught the "Euro-stlye" for set proofs. Of course, my experience is extremely limited.
strangequark I learned my epsilon the same way bud.
To keep this thread going at 2 posts a year, I will say it is very unlikely mathematicians are to blame for the two styles of epsilon. I haven't looked it up, but mathematicians are not typographers, and use the fonts that are available, except where special symbols are created in manuscript. I bet the two epsilons arose outside maths.
This has puzzled me for quite a while now, and I can't seem to find a clear answer to this. When writing mathematical texts (in LaTeX, say), people often use the symbol epsilon, e.g. denoting some small positive variable. However, some people use the epsilon-version with a straight back (similar to the \in symbol), while others use the one with a curly back (the reversed 3). Why?? Why use one instead of the other? Why is one of them better? And why have two different ways to write it?