quadrangle= a four-sided enclosure, usually surrounded by buildings

 

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 that is located along the front of the thigh 

 

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

 

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 nor from the same mother at the same time