retention /riten″shən/ , 1. a resistance to movement or displacement. 2. the ability of the digestive system to hold food and fluid. 3. the inability to urinate or defecate. 4. the ability of the mind to remember information acquired from reading, observation, or other processes. 5. the inherent property of a dental restoration to maintain its position without displacement under axial stress. 6. a characteristic of proper tooth cavity preparation in which provision is made for preventing vertical displacement of the cavity filling. 7. a period of treatment during which an individual wears an appliance to maintain teeth in positions to which they have been moved by orthodontic procedures. −retain, v.