Groove (engineering) in the context of "Rotating spline"

Tramway track is used on tramways or light rail operations. As with standard rail tracks, tram tracks have two parallel steel rails, the distance between the heads of the rails being the track gauge. When there is no need for pedestrians or road vehicles to traverse the track, conventional flat-bottom rail is used. However, when such traffic exists, such as in urban streets, grooved rails are used.

Tram rails can be placed on several surfaces, such as on ground over which track ballast topped by sleepers (US: ties) and flat-bottom rails are laid – as with railway tracks – or, for street running, with grooved rails usually embedded into a concrete pavement. In some places, tracks are laid into grass turf surfaces; they are known as green track, grassed track or track in lawn.

In mechanical engineering, a rolling-element bearing, also known as a rolling bearing, is a bearing which carries a load by placing rolling elements (such as balls, cylinders, or cones) between two concentric, grooved rings called races. The relative motion of the races causes the rolling elements to roll with very little rolling resistance and with little sliding.

One of the earliest and best-known rolling-element bearings is a set of logs laid on the ground with a large stone block on top. As the stone is pulled, the logs roll along the ground with little sliding friction. As each log comes out the back, it is moved to the front where the block then rolls onto it. It is possible to imitate such a bearing by placing several pens or pencils on a table and placing an item on top of them. See "bearings" for more on the historical development of bearings.