| A | B |
| quadrangle | a four-sided enclosure, usually surrounded by buildings |
| quadrant | one 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 asquare, 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 born from the same mother at the same time |