Headway
Part of speech: noun
Definition: Forward motion, or its rate. The interval of time or distance between the fronts of two vehicles (e.g. buses) moving in succession in the same direction, especially along the same pre-determined route. Progress toward a goal. The clearance beneath an arch, ceiling or bridge; headroom.
Headroom
Part of speech: noun
Definition: the vertical clearance above someone's head, as in a tunnel, doorway etcthe ability of a system to reproduce loud sounds free of distortion; dynamic headroom