quadratic

Involving a squared variable and nothing higher — degree 2.

An expression or equation is quadratic when its highest power of the variable is 2, the general form being $ax^2+bx+c$ with $a \neq 0$ . "Quad-" comes from the Latin for "four," a nod to the four-sided area a squared term once represented geometrically.

Examples

$x^2-5x+6=0$ is a quadratic equation; $2x-7=0$ is not (no squared term).