An illness is defined as a period of sickness affecting the body or mind and can include disease (both communicable and congenital), disorders (both physical and mental), and poisoning (accidental exposure, ingestion of contaminated comestibles). Illness can be described as feeling ill, which can be caused by lack of nourishment, overindulgence, dehydration, sleep deprivation, and overexposure to heat, although these are not typically considered a disease, a disorder, or poisoning.