diaita

Diaita is a Greek term denoting a regimen or way of life, with emphasis on daily practices such as diet, exercise, sleep, and moral conduct. In classical and later medical and philosophical literature, diaita referred to the organized pattern of living prescribed to promote health and well-being or to control disease. The word is commonly translated as "regimen" or "diet," though its sense encompasses lifestyle habits beyond mere food.

In the Hippocratic Corpus, diaita is a central therapeutic tool: physicians prescribe a patient’s diet, rest, physical activity, and environmental conditions as part of treatment. Galen and later physicians developed the concept into formal dietetics, detailing regimens tailored to illness, constitution, climate, season, and age. Beyond medicine, diaita also appeared as a broader notion of virtuous living in philosophical writers who discussed how daily habits shape character and happiness.

Today, diaita survives in scholarly discussions of ancient medicine as a term for therapeutic lifestyle regimes; in modern Greek it retains a sense closely aligned with "diet" or "regimen." The English term "diet" ultimately derives from a Latinization of diaita via diaeta, reflecting the word’s long association with regulated daily living.