[and one more...] In reply to the question from Oswald Wyler <owyler@suscom-maine.net> let me quote from Donald E. Knuth, The Art of Computer Programming (1968, 1973), Section 1.2.8: The number $\phi$ itself has a very interesting history. Euclid called it the "extreme and mean ratio"; the ratio of A to B is the ratio of (A+B) to A, if the ratio of A to B is $\phi$. Renaissance writers called it the "divine proportion"; and in the last century it has commonly been called the "golden ratio". In the art world, the ratio of $\phi$ to 1 is said to be the most pleasing proportion aesthetically, and this opinion is confirmed from the standpoint of computer programming aesthetics as well. For the story of $\phi$, see the excellent article "The Golden Section, Phyllotaxis, and Whythoff's Game", by H.S.M. Coxeter, Scripta Math. 19 (1953), 135-143, and see also Chapter 8 of The 2nd Scientific American Book of Mathematical Puzzles and Diversions, by Martin Gardner (New York: Simon and Schuster, 1961). -- Nils Andersen
In seventh or eighth grade -- a long time ago -- , I learned the name "goldener Schnitt" (golden ratio, ratio aurea) for the positive solution of the equation x^2 = x + 1. Recently, I read an article, I forgot where, discussing this number and using \phi as the "accepted symbol" for it. The old name was never mentioned.
So far, I have only met three real or complex numbers with universally accepted one-letter symbols: \pi, e, i. Have I missed something?
Oswald Wyler