In medicine, describing a disease as acute denotes that it is of recent onset; it occasionally denotes a short duration. The quantification of how much time constitutes "short" and "recent" varies by disease and by context, but the core denotation of "acute" is always qualitatively in contrast with "chronic", which denotes long-lasting disease (for example, in acute leukaemia and chronic leukaemia).

In the context of the mass noun "acute disease", it refers to the acute phase (that is, a short course) of any disease entity.^[1][2] For example, in an article on ulcerative enteritis in poultry, the author says, "in acute disease there may be increased mortality without any obvious signs",^[3] referring to the acute form or phase of ulcerative enteritis.

A mild stubbed toe is an acute injury. Similarly, many acute upper respiratory infections and acute gastroenteritis cases in adults are mild and usually resolve within a few days or weeks.^{[citation needed]}

The term "acute" is also included in the definition of several diseases, such as severe acute respiratory syndrome, acute leukaemia, acute myocardial infarction, and acute hepatitis. This is often to distinguish diseases from their chronic forms, such as chronic leukaemia, or to highlight the sudden onset of the disease, such as acute myocardial infarct.^[2]

Related terms include:

Acute care is the early and specialist management of adult patients who have a wide range of medical conditions requiring urgent or emergency care usually within 48 hours of admission or referral from other specialties.^[2]

Acute hospitals are those intended for short-term medical and/or surgical treatment and care which is a medical speciality of acute medicine, as often primary care is not positioned to assume this role.^[12]

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