If you have ever been on board of a ship, you know that the left and right sides have special names. They are respectively port and starboard, if you are standing aboard facing the front (or the bow) of the vessel.

Most boats are symmetrical along their length. One asymmetric feature is where to access the boat, usually on the port side (hence the name).

The words port and starboard come from medieval Latin. In the early days of boating, before ships had rudders on their centre lines, boats were controlled using a steering oar. Most sailors were right-handed, so the steering oar was placed over or through the right side of the stern. Sailors began calling the right side the steering side, which soon became ‘starboard’ by combining two Old English words: stéor (meaning ‘steer’) and bord (meaning ‘the side of a boat’).

Over time, larboard ‒ too easily confused with starboard ‒ was replaced with port

As the size of boats grew, so did the steering oar, making it much easier to tie a boat up to a dock on the side opposite the oar. This side became known as larboard, or ‘the loading side’. Over time, larboard ‒ too easily confused with starboard ‒ was replaced with port. After all, this was the side that faced the port, allowing supplies to be ported aboard by porters.

Port and starboard unambiguously refer to the left and right side of the vessel, not the observer. In other words, the vessel’s port side always refers to the same portion of the vessel’s structure, and does not depend on which way the observer is facing; unlike left and right.

When travelling at night, port and starboard can be identified by red and green lights respectively (this is easy to remember as red is the colour of Port wine).