World Health Organization (WHO) defined health as "a state of complete physical, mental and social well–being and not merely the absence of disease or infirmity" which was later modified to include the ability to lead a "socially and economically productive life". In the medical field, the technical term for health is homeostasis, an organism's ability to efficiently respond to challenges (stressors) and effectively restore and sustain a "state of balance". Health care is the prevention, treatment and management of illness and the preservation of mental and physical well being through the services offered by the medical, nursing and allied health professionals.

Nutrition is the science that studies how what people eat affects their health and performance, foods and dietary supplements that improve performance, promote health, and cure or prevent disease. Diet such as fresh fruits, vegetables, and foods rich in certain fatty acids may foster a healthy immune system, which protects the body from infection, disease, or other unwanted biological invasion. An immune system is a collection of mechanisms within an organism that protects against disease by identifying and killing pathogens and tumor cells.

Diagnosis is the recognition of a disease or condition by its outward signs and symptoms and analysis of the underlying physiological/biochemical cause(s) of a disease. Medical tests commonly performed are measuring blood pressure, checking pulse rate, listening to the heart with a stethoscope, blood tests, medical imaging and electrocardiogram.

Medicine is the sceince and art of maintaining and/or restoring human health through the study, diagnosis and treatment of patients. The modern practice of medicine occurs at the many interfaces between the art of healing and various sciences. Working together as an interdisciplinary team, many highly trained health professionals besides medical practitioners are involved in the delivery of modern health care. Some examples include: nurses, laboratory scientists, pharmacists, physiotherapists, radiographers, dietitians,and biomedical engineers. The greatest inventions in the field of medicine over a period of time include surgical needle thermometer, stethoscope, vaccination, anesthetics, electrocardiograph, sphygmomanometer, pencillin, pacemaker, ultrsound scan, MRI enhanced the health care.