- a short time to take effect, as in acute infection
- a short "course" (as opposed to a chronic course, which is something which lasts a long time).
The word acute may often be confused by the general public to mean 'severe'. This is different and something can be acute but not severe.
Subacute is described as between acute and chronic. An example is subacute fever symptoms or subacute endocarditis.
Chronic is the opposite of acute. Chronic means a long term condition, for example chronic bronchitis. Chronic may also be confused by people who do not work in medicine to mean severe. Again, this is a different thing medically and something can be chronic but not severe.