This list of ship directions explains dozens of related terms such as fore, aft, astern, aboard, or topside. For background, see below: Origins.
abaft (preposition): at or toward the stern of a ship, or further back from a location, e.g. the mizzenmast is abaft the mainmast.aboard: onto or within a ship, or in a group.above: a higher deck of the ship.aft (adjective): toward the stern of a ship.adrift: floating in the water without propulsion.aground: resting on the shore or wedged against the sea floor.ahull: with sails furled and helm lashed alee.alee: on or toward the lee (the downwind side).aloft: the stacks, masts, rigging, or other area above the highest solid structure.amidships: near the middle part of a ship.aport: toward the port side of a ship (opposite of "astarboard").ashore: on or towards the shore or land.astarboard: toward the starboard side of a ship (opposite of "aport").astern (adjective): toward the rear of a ship (opposite of "forward").athwartships: toward the sides of a ship.aweather: toward the weather or windward side of a ship.aweigh: just clear of the sea floor, as with an anchor.below: a lower deck of the ship.belowdecks: inside or into a ship, or down to a lower deck.bilge: the underwater part of a ship between the flat of the bottom and the vertical topsidesbottom: the lowest part of the ship's hull.bow (or stem): front of a ship (opposite of "stern")centerline: an imaginary, central line drawn from the bow to the stern.fore or forward: at or toward the front of a ship or further ahead of a location (opposite of "aft")inboard: attached inside the ship.keel: the bottom structure of a ship's hull.leeward: side or direction away from the wind (opposite of "windward").on deck: to an outside or muster deck (as "all hands on deck").on board: somewhere on or in the ship.outboard: attached outside the ship.port: the left side of the ship, facing forward (opposite of "starboard").starboard: the right side of the ship, when facing forward (opposite of "port").stern: the rear of a ship (opposite of "bow").topside: on the ship's main weather deck.underdeck: a lower deck of a ship.yardarm: an end of a yard spar below a sail.waterline: where the water surface meets the ship's hull.weather: side or direction from which wind blows (same as "windward").windward: side or direction from which wind blows (opposite of "leeward").First use of "aboard": 14th centuryFirst use of "aft": 1580First use of "outboard": 1694First use of "inboard": 1830First use of "belowdecks": 1897.The word "ahoy" is not a direction, but rather an interjection used to hail a person or ship, or to attract attention. See the linked sources, below, for more details.
