The words "pier," "slip," "dock," "wharf," etc., have or had very specific meanings. A true "dock" is the same as a slip. A dock, or slip, is an inlet of water large enough to contain one or more ships. A dock is basically an enclosed area of water large enough to hold a ship; a dock is not a wharf or pier, although it has now, incorrectly, come to mean that. Manhattan had many slips in the 18th century. These were replaced beginning about 1790 with a system of projecting piers, or wharfs that projected into the harbor to which ships could tie. A quay is a wharf that is built parallel with the water's edge, to which a ship can tie. A wharf is basically any built structure to which a ship can tie. I am curious to know why the word "slip," in the meaning of dock, is not included in the Oxford English Dictionary. It is, I think, clearly an English language word. Paul Huey