| Term | Definition | Pronunciation |
| qrs complex | A segment of an EKG tracing representing ventricular depolarization. | |
| qt | quart | |
| quackery | The fraudulent misrepresentation of the diagnosis and treatment of disease. | |
| quadr- | four | |
| quadri- | four | |
| quadriceps muscle | The quadriceps femoris. A collective name of the four-headed skeletal muscle of the thigh. | |
| quadriplegia | Paralysis that results in the partial or total loss of use of all four limbs and torso. | kwod″rĭ-ple´jah |
| quantum theory | The theoretical basis of modern physics that explains the nature and behavior of matter and energy on the atomic and subatomic level. | |
| quarantine | The isolation of individuals who have been exposed to an infectious disease in order to prevent its spread. | |
| quasi | virtual, resembling | |
| quickening | Movements of the fetus felt by the mother, usually after the first 16 weeks of pregnancy. | |
| quinine | An drug derived from the bark of the cinchona tree, used as an antimalarial drug. | |
| quint/i | fifth | |