Psychiatry is the part of medicine that studies and treats mental illness. It is the field, not the person — the person is a psychiatrist. In a hospital, psychiatry is the department that helps people whose minds are unwell, with medicine, with talking, or with both. People often set it next to psychology as if the two were twins. Though actually they are not. Psychology is the wider study of how people think and feel, including healthy people. Psychiatry is specifically medical: illness, diagnosis, treatment. The English word was borrowed from French psychiatrie. We first see it in English in 1846, so it is a fairly modern medical name, not an old farm-and-hearth word.