WBC count, or white blood cell count, measures the number of leukocytes in a specified volume of blood, typically expressed in cells per microlitre. It is crucial in diagnosing and monitoring infections, inflammatory conditions, and hematological disorders, as abnormal levels can indicate underlying pathologies. For example, a high WBC count may suggest an acute infection or leukaemia, while a low count could indicate bone marrow suppression or autoimmune diseases.