A "diagnostic" refers to a process or tool used to identify a problem or condition. In medicine, diagnostics often involve tests and examinations that help healthcare professionals determine the nature of a patient's illness. Common diagnostic methods include blood tests, imaging scans, and physical examinations. In other fields, such as education or technology, diagnostics can assess performance or functionality. For example, educational diagnostics may evaluate a student's learning needs, while software diagnostics identify issues within a program. Overall, diagnostics play a crucial role in understanding and addressing various challenges across different domains.