Quad- means four

quadrangle (n) - a four-sided enclosure, usually surrounded by buildings

quadrant (n) - one out of four equal parts of a circle; one section of a four-section coordinate grid

quadrennial (adj) - happening every four years

quadriceps (n) - a muscle group consisting of four muscles that is located along the front of the thigh

quadrilateral (n) - a plane figure in geometry that has four sides (including square, rectangle, rhombus, parallelogram, and trapezoid)

quadrilingual (adj) - the ability to speak four languages

quadrisect (v) - to cut or divide into four equal parts

quadruped (n) - an animal with four feet

quadruple (v) - to create four times as much or as many of something

quadruplet (n) - a collection of four; one of four babies born from the same mother at the same time