"Negative marking" refers to a penalty system in exams where incorrect answers result in a deduction of marks from the total score. In the context of the UPSC preliminary exam, candidates lose a specified number of points for each wrong answer selected. This system encourages thoughtful selection and discourages random guessing, thus promoting a deeper understanding of the syllabus material. It emphasizes the importance of careful preparation to minimize errors and optimize overall performance in the highly competitive examination.