quadrangle

a four-sided enclosure, usually surrounded by bulidings

quadrant

one out of four equal parts of a circle; one section of a four-section coordinate grid

quadrennial

happening every four years

quadriceps

a muscle group consisting of four muscles located along the front of the thigh

quadrilateral

a plane figure in geometry that has four sides

quadrilingual

the ability to speak four languages

quadrisect

to cut or divide into four equal parts

quadruped

an animal with four feet

quadruple

to create four times as much or as many of something

quadruplet

a collection or group of four; one of four babies born from the same mother at the same time.