FUNCTION

FUNCTION, in Analysis, denotes an algebraical expression in any way compounded of a certain letter or quantity with other quantities or numbers; and the expression is said to be a function of that letter or quantity. Thus

$a\; =\; 4x$, or $ax\; +\; 3x^2$, or $2x\; -\; a\backslash sqrt\{a^2\; -\; x^2\}$, or $x^c$, or $e^x$, is each of them a function of the quantity $x$.