ROOT, in Algebra and Arithmetic, denotes any number which, multiplied by itself once or oftener, produces any other number; and is called the square, cube, bi-quadratic, &c. root, according to the number of multiplications. Thus, 2 is the square of 4; the cube-root of 8; the bi-quadratic root of 16, &c.
ROOT of an equation, denotes the value of the unknown quantity in an equation, which is such a quantity, as being substituted instead of that unknown letter, into the equation, shall make all the terms to vanish, or both sides equal to each other. Thus, of the equation , the root or value of is 3, because substituting 3 for makes it become .