On ships, the directions "right" and "left" are not commonly used. Instead, mariners use nautical terms. Starboard is the right-hand side of the ship as seen from someone facing the bow, or front, of the ship. Port is the opposite of starboard, or the left side of the ship. One benefit of using these nautical terms is that starboard and port do not change depending on which direction a person is facing.

The etymology of the word "starboard" is fairly straightforward. The word comes from a combination of two Old English words: stéor, meaning "steer" and bord, meaning "the side of a boat or a ship." The rudder, used to steer a ship, was originally on the right-hand side of a ship. The term stéorbord, "the steering side of a ship," later became starboard.

The opposite of starboard was larboard, or "the loading side." This was too easily confused with its rhyming opposite, starboard, so was later changed to port. This term may have come from the fact that cargo was routinely loaded from the port onto the left-hand side, or from the Latin words for harbor or door. The term "port" was officially accepted over "larboard" by Britain's Royal Navy in the 1840s. The term "starboard" remained and continues to remain in use.

The starboard side of most ships is usually the "senior" side, with the flag of the captain being raised on this side. The starboard side of the quarterdeck is generally reserved for the captain, and if the ship carries its own gangway, the officers' gangway is stored on the starboard side.

On seagoing vessels, as well as aircraft, the starboard side is designated with a green light, while the port side has a red light. A white light is mounted on the aft or rear side of the ship. This is true of ships around the world.

Many landlubbers have trouble remembering which side of a ship is starboard and which is port. One mnemonic device is to remember that port wine is generally red, so port has a red light and starboard must have a green one. Another is to be aware that "left" comes before "right" in the alphabet, and "port" comes before "starboard." Or that "left" has four letters, so it must match with the other four-letter word, which is "port" and not "starboard." Of course, all these clues only work when a person is facing the front of a ship.