An Etymological Dictionary of Astronomy and Astrophysics

If a function φ(x) is continuous on a closed interval [a,b], then for every ε > 0 there exists a polynomial P(x) such that |f(x) - P(x)| <ε, for every x in the interval.

See also: After German mathematician Karl Wilhelm Theodor Weierstrass (1815-1897); → approximation; → theorem.