But in that case, it also isn’t really a variable, though. The other usage I can think of is in denoting unit vectors—e[sub]x[/sub], e[sub]y[/sub], and e[sub]z[/sub], for example. But that’s also not really a variable.
I suppose that the Greek letters that look exactly like Latin letters are probably the least common, because why would you use the Greek one? So omicron is probably the least-used.
And I once graded a student who used Cyrillic letters for his auxiliary variables (he was from somewhere in Eastern Europe). It did guarantee that none of his variables were already in use in the problem, but it took me a while to realize that ш and щ were two different letters.
For Greek letters, I expect the omicron to be the least used, for the same reason o is rarely used among the Latin letters.
ETA: ninja’d [curse you Chronos]
Cyrillic probably would take the cake for most confusing variable if somebody were to use З (ze), though.
Sure it is. It’s a placeholder to whatever the identity value is. It might stand for 1, it might stand for 0, it might stand for +∞, etc.
You’re stating a theorem in Group Theory and it goes “blah, blah, blah, e, blah, blah, blah.” e here serves the same function as a x does in Real Analysis where a theorem states “blah, blah, blah, x, blah, blah, blah.”
This is unlike, say, in Computer Science where e or something like it* refers to the empty string. An empty string is a fixed value. A string of length zero. That is a constant.
- I prefer λ myself.
One of my engineering professors referred to zeta as “the Greek letter squiggly”.
It’s no more squiggly than a (handwritten) Latin z, is it? At least not in my handwriting. Also, letters are not “drawn”— they are written (at least when they’re not typed, printed, etc.)
Besides the famous ζ-function, I want to say I recall very typical uses along the lines of: let ζ be a primitive nth root of unity, and consider the cyclotomic field Q(ζ)…
I was looking at the properties of 2019 OK* yesterday and noticed another use of e as a variable: eccentricity of orbit.
Even for a given object, e is not a fixed value. For example the eccentricity of Mars changes over time a surprising amount.
And 2019 OK’s eccentricity had to have gotten a big change when it passed us by 0.19 lunar distances the other day.
Another use in Physics is good old e = mc[sup]2[/sup]. Two out of the 3 are variables.
It’s also used as the symbol for electron charge but that’s a constant. Oddly, m is also used for the mass of an electron. Figuring out e/m was a notable early Physics measurement. (I did this measurement in E&M lab in college. Um, that’s Electricity and Magnetism, resp.)
- Happening to get the sequence label “OK” for an asteroid that passed this close catches the eye. It’s impact energy would have been 30 Hiroshima A-bombs.
When it stands for energy, E is generally capitalized. Likewise for when it’s electric field. You’re right, though, that eccentricity is usually lower-case e.
m for mass is pretty typical. What it’s the mass of is generally made clear by context. In finding the e/m ratio, the context is electrons, but in a problem about a baseball, it’s probably the mass of a baseball.
ftg, the empty string isn’t any more a constant than the identity element of an arithmetic is. In fact, the empty string is itself the identity element of concatenation. But the empty string in C isn’t the same as the empty string in Fortran isn’t the same as the empty string in Java, and an empty Unicode string isn’t the same as an empty ASCII string, and so on. But once you’ve set the context, the empty string (or the identity element) is well-defined and unique.
i is another good candidate for similar reasons: it’s the square root of -1
Word on the street is that Ladies Love Cool J.
But i is one of the standard default variable names in any sort of discreet mathematics, like as an index for an array. And, as mentioned, it often gets used for current (physicists usually capitalize it for current, but engineers might or might not).
Shh, don’t tell!
Those are implementations of a constant. Not the constant itself.
You don’t think of π as a non-constant just because it is represented in different ways on a computer do you?
I must say I am amazed you made this statement. It is silly.
I suspect it is o. I don’t think I ever used it and I use all the others all the time. When I use l, though, it is not an ordinary l, but one with a loop like a handwritten l.
One thing I would like to clarify is that mathematical journals no longer distinguish typographically between constants and variables. Once upon a time, constants were set upright and variables in italics. But typesetters can’t tell what is intended. Nowadays (and this is strongly enforced by the journal I am TeX editor for) single letter identifiers are set in italics (specifically, math italics which differ somewhat from text italics), while multicharacter identifiers such as sin, log, and the like are set upright. So sin is just the product sin, while sin is just the standard trigonometric function.
For Greek letters, needless to say, the only capitals used are those that differ from the roman capitals. How could you tell a Rho from a P? All the lower case Greek letters are common, again except omicron. The least used capital is probably Xi (which consists of three horizontal lines), although I have seen it and even used it. I don’t find either xi or zeta hard to write or to recognize.
I am told that Russian mathematicians use roman and greek alphabets for their identifiers, but not usually cyrillic. I once heard a talk by the Russian Yuri Matiyasevich talking about the equation he had discovered in connection with his solution to Hilbert’s 10th problem. The first unsolvable equation he had discovered had something like 32 variables. Finally, he had found one with only 26 and he was happy because that meant that he could write it using only the roman alphabet (so one of them had to be o).