A slipway is a sloping track, usually of concrete, stone, or timber, that runs down into the water so boats can be moved in or out. You see one at a small harbour, a boatyard, or a ferry slip: the boat is winched or slid down the slope until it floats, or pulled back up onto land. Shipyards use a bigger slipway to launch a newly built ship — the hull sits on the slope, the blocks are knocked away, and it slides into the water. The slope is the point. A dock or a quay is a wall you tie up to; a slipway is a ramp you travel along. In some places people just say slip for the same kind of landing, especially a ferry slip. The word belongs to boats and yards, not to ordinary roads. You would not call a wheelchair ramp a slipway. It is a practical, slightly technical word: harbour notices, sailing clubs, and news about a launch will use it without explaining. Though actually, the “slip” here is not a mistake and not a banana skin. It is the old idea of sliding — the boat slips down the way into the water.

船台、下水滑道（讓船沿著斜坡滑進或拉出水面的軌道）