We can classify a disease for example according to the severity (mild, intermediate, and severe) or according to the stability (stable and non-stable) and so on. According to what we determine acute and chronic?
The symptomatic timeframe of the disease from onset through healing can be described as acute or chronic. Acute can mean that the disease has a short symptomatic cycle. The disease comes on quickly and can be healed quickly (in a matter of weeks). Chronic can mean the disease will remain symptomatic over a long period of time. It may last through the rest of the patient’s life. There may be times of greater or lesser severity in a chronic disease. But, it is always present for the possibilities of flare-ups.
Usually they are classified under the phases or stages of a disease.
According to the phase or stage of disease: 1. Acute. 2. Chronic.
See also here: stage of the condition (https://www.physio-pedia.com/Stage_of_the_Condition)