On a ship, a companionway is the stairs — often steep, more like a ladder with steps — that take you from one deck to another, from the open top down into the rooms below, or from one inside level to the next. It is a sailors’ word, not a word for stairs in a house or a mall. You go up or down it, usually holding a rail, and it can feel sharp when the sea rolls. You will see it in writing about boats, the navy, and travel by ship, almost never in city life. Though actually the first half looks like “friend,” this is not a path you walk with a friend on land; it is only the ship’s stair-passage.