Kilometre per hour (km/h) is the standard metric unit of speed that quantifies how many kilometres an object travels in one hour, symbolized as km/h or km·h⁻¹; it is widely used in road signage, vehicle performance specifications, and scientific calculations to convey motion in everyday and technical contexts. By measuring distance over time, km/h provides a clear, universally understood reference for drivers, cyclists, and engineers, enabling accurate navigation, safety compliance, and performance analysis. Its adoption across international transportation systems and scientific research underscores its importance for precise speed reporting, fuel efficiency assessments, and aerodynamic studies, making kilometre per hour an essential metric for both practical everyday use and rigorous scientific inquiry.