Which of the following is an example of a symptom?

A symptom is typically defined as a subjective experience or feeling reported by the patient, which indicates an underlying condition. Nausea fits this definition as it is a sensation experienced by the individual and cannot be measured directly by someone else; rather, it relies on the person's account of their feelings.

In contrast, options like fever, cyanosis, and swelling are generally categorized as signs. A fever is a measurable increase in body temperature, cyanosis refers to a bluish discoloration of the skin indicating decreased oxygenation, and swelling is a physical condition observable by others. These are objective indicators of medical issues that can be assessed by healthcare professionals without requiring the patient's description of their experience. Therefore, nausea stands out as a true symptom among the choices.