What is the term for the process of determining the nature of a person's disease?

The process of determining the nature of a person's disease is referred to as diagnosis. This term specifically describes the method by which healthcare professionals identify a disease or condition based on the symptoms, medical history, and any necessary tests or examinations.

Diagnosis is crucial in the medical field as it informs the subsequent treatment plan and management of the patient’s condition. It involves critical analysis and reasoning to distinguish one illness from another and to understand the underlying factors contributing to a patient's symptoms.

Other terms like prognosis, assessment, and evaluation, while related to patient care, serve different functions. Prognosis deals with predicting the likely outcome of a disease after a diagnosis has been made. Assessment may involve gathering various pieces of information regarding a patient’s health status and might include a broader scope of data collection, while evaluation typically refers to the analysis of the effectiveness of a treatment or intervention. Thus, the definition and role of diagnosis are central to the overall process of healthcare delivery.