From Prelude to Mathematics by W. W. Sawyer (1955):
There must be many universities today where 95 percent, if not 100 percent, of the functions studied by physics, engineering, and even mathematics students, are covered by the single symbol F(a, b; c; x).
The symbol Sawyer refers to is the hypergeometric function. (There are hypergeometric functions with any number of parameters, but the case with three parameters is so common that it is often called “the” hypergeometric function.) The most commonly used functions in application — trig functions, exp, log, the error function, Bessel functions, etc. — are either hypergeometric functions or closely related to hypergeometric functions. Sawyer continues:
I do not wish to imply that the hypergeometric function is the only function about which mathematics knows anything. That is far from being true. … but the valley inhabited by schoolboys, by engineers, by physicists, and by students of elementary mathematics, is the valley of the Hypergeometric Function, and its boundaries are (but for one or two small clefts explored by pioneers) virgin rock.