Which term describes an illness that arises quickly and can be expected to go away?

An illness that arises quickly and is expected to resolve within a relatively short period is termed an acute illness. Acute illnesses can manifest suddenly and typically have a clear onset, often characterized by symptoms that may be severe but are short-lived. Common examples include conditions like the flu, a broken bone, or an asthma attack, which require immediate attention but can generally be treated effectively leading to recovery.

Chronic illnesses, on the other hand, develop gradually and persist over a long period, often for the rest of a person's life. Terminal illnesses are progressive conditions that are expected to lead to death, and developmental disorders are conditions that affect physical, learning, language, or behavioral growth. These other terms do not encompass the characteristics of a condition that appears suddenly and improves over time, making acute illness the correct classification in this scenario.