40 m/s describes the speed of an object
speed is rate_of_motion. speed is motion. speed is not rate_of_motion. measure_of_speed is measuring_event. unit_of_speed is kilometers_per_hour. measure_of_speed is not measuring_event. speed is rate. speed_of_light is approximately_299792458_metres_per_second. unit_of_speed is not kilometers_per_hour.