senility (sənilˈətē) [key], deterioration of body and mind associated with old age. Indications of old age vary in the time of their appearance. Stooped posture, wrinkled skin, decrease in muscle strength, changes in the lens and muscles of the eye, brittleness of bone and stiffness of the joints, and hardening of the arteries (arteriosclerosis) are among the physical changes associated with old age. The mental changes associated with senility include impairment of judgment, loss of memory, and sometimes childish behavior. The psychological changes are thought to be related to aging of the cortical brain cells. Whereas the physical changes associated with aging occur in all individuals to some extent, evidence of psychological degeneration is not universal. In common usage, the term senility is applied only to mental deterioration. See geriatrics; Alzheimer's disease; amnesia.