- cotoA traditional Spanish unit of length, equivalent to about 10.4 cm.
- quad-Involving four elements.
- quadriporticusA nearly square courtyard surrounded by colonnaded porticoes.
- quadriviumThe higher division of the seven liberal arts in the Middle Ages, composed of geometry, astronomy, arithmetic, and music.
- quattuordecupleFourteenfold.
- quattuorquadragintillion10¹³⁵.
- quattuortrigintillion10¹⁰⁵.