Disease Definition

Definition of Disease

Disease (Latin dis- = lack of, opposite of + ease = convenience, comfort) literally means lack of strength or satisfaction. It also means a person is no longer at ease.

In medicine, disease means an impairment in structure or function of a certain body part or mind with identifiable symptoms or signsMorbus is a Latin word for disease. This is ideal definition but disease should be seen as any temporary or permanent disturbance in the body that disrupts the state of balance in the body (homeostasis). This balance necessary for a person to be in good health and function optimally.

Illness, Sickness, Malady, Malaise

When referring to patient’s personal experience of a disease, synonyms illness and sickness are usually used. Ailment refers to minor or chronic illness. Malady (French malady = disease) refers to chronic or deep-seated disease. Malaise (French mal- = bad; aise= ease) is a vague feeling of general weakness and discomfort, commonly appearing at the onset of an illness.


Anomaly (Gk. an-= not, homalos = even) is a deviation from normal, ‘not the same’, usually used in abnormal organ development. For example, congenital anomaly means an abnormality present from birth.


In medicine, disorder means abnormal function of the body, either an organ, system or the body as a whole.


Physical or mental disability is an inborn or acquired disadvantage or deficiency that prevents or restricts normal achievement.

Inborn Error

An inborn error is a defect present from birth, causing a disease or disability or sometimes there is none of these and functioning continues as normal.


An injury or trauma is damage to the body structure or function caused by a physical force, heat, cold, chemicals, electricity, or irradiation, usually affecting the body from the outside. Examples: wound, bruise, concussion, bone fracture.


Infection is an invasion of pathogenic microbes into the body. It may be superficial, occurring in the skin and surrounding layers, or deep-seated occurring within the body. It is often localized meaning that it is restricted to just one area or it can be systemic where the pathogen has spread to multiple distant sites or even the whole body.

Lethal or Life-Threatening

Lethal means deadly. In medicine the word life-threatening is often used for a condition that has the potential to cause death but may not do so in every case. Lethal usually indicates that death is definite.


Poisoning is a disturbance caused by chemical reaction of certain substances (poisons) on the molecular level. For example, when carbon monoxide is inhaled, it binds to hemoglobinin thus preventing binding of oxygen, resulting in inadequate supply of oxygen to the body, and, eventually, death.

Pathological, Pathogenic

Pathological (Greek pathos = suffering; logia = study) means ‘related to disease’.

Pathogenic means ‘capable of causing disease’. Example: pathogenic bacteria.

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