甲板通常指船只上位于隔间或船体上面的永久覆盖物，多为露天设计。在艇或船上，主甲板是构成船体顶部的水平结构物，既可强化船体，也可供人员在上面行走或工作。轮船通常有超过一层的平面，可以是在船体内，也可以在主甲板上的上层结构内，类似多层大厦的各楼层，它们有时也被称为甲板。

A deck is a permanent covering over a compartment or a hull of a ship. On a boat or ship, the primary or upper deck is the horizontal structure which forms the 'roof' for the hull, which both strengthens the hull and serves as the primary working surface. Vessels often have more than one level both within the hull and in the superstructure above the primary deck which are similar to the floors of a multi-storey building, and which are also referred to as decks, as are specific compartments and decks built over specific areas of the superstructure. Decks for some purposes have specific names.