
Port and starboard are
nautical terms for
watercraft and
aircraft, referring respectively to the left and right sides of the vessel, when aboard and facing the
bow (front).
Vessels with bilateral
symmetry
Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ...
have left and right halves which are
mirror image
A mirror image (in a plane mirror) is a reflected duplication of an object that appears almost identical, but is reversed in the direction perpendicular to the mirror surface. As an optical effect it results from reflection off from substances ...
s of each other. One asymmetric feature is where access to a boat, ship, or aircraft is at the side, it is usually only on the port side (hence the name).
Side
Port and starboard unambiguously refer to the left and right side of the vessel, not the observer. That is, the port side of the vessel always refers to the same portion of the vessel's structure, and does not depend on
which way the observer is facing.
The port side is the side of the vessel which is to the left of an observer aboard the vessel and , that is, facing forward towards the direction the
vehicle is heading when
underway, and starboard side is to the right of such an observer.
This convention allows orders and information to be given unambiguously, without needing to know which way any particular crew member is facing.
Etymology

The term ''starboard'' derives from the
Old English
Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlement of Britain, Anglo ...
''steorbord'', meaning the side on which the ship is steered. Before ships had
rudders on their centrelines, they were steered with a
steering oar
The steering oar or steering board is an over-sized oar or board, to control the direction of a ship or other watercraft prior to the invention of the rudder.
It is normally attached to the starboard side in larger vessels, though in smaller ...
at the
stern
The stern is the back or aft-most part of a ship or boat, technically defined as the area built up over the sternpost, extending upwards from the counter rail to the taffrail. The stern lies opposite the bow, the foremost part of a ship. Ori ...
of the ship on the right hand side of the ship, because more people are
right-handed.
The "steer-board" etymology is shared by the
German ''Steuerbord,''
Dutch ''stuurboord'' and
Swedish
Swedish or ' may refer to:
Anything from or related to Sweden, a country in Northern Europe. Or, specifically:
* Swedish language, a North Germanic language spoken primarily in Sweden and Finland
** Swedish alphabet, the official alphabet used by ...
''styrbord'', which gave rise to the
French
French (french: français(e), link=no) may refer to:
* Something of, from, or related to France
** French language, which originated in France, and its various dialects and accents
** French people, a nation and ethnic group identified with Franc ...
''tribord'',
Italian ''tribordo,''
Catalan ''estribord'',
Portuguese ''estibordo'', Spanish ''estribor'' and
Estonian
Estonian may refer to:
* Something of, from, or related to Estonia, a country in the Baltic region in northern Europe
* Estonians, people from Estonia, or of Estonian descent
* Estonian language
* Estonian cuisine
* Estonian culture
See also ...
''tüürpoord''.
Since the steering oar was on the right side of the boat, it would tie up at the
wharf on the other side. Hence the left side was called ''port''. The ''
Oxford English Dictionary'' cites ''port'' in this usage since 1543.
Formerly, ''larboard'' was often used instead of ''port''. This is from
Middle English ''ladebord'' and the term ''lade'' is related to the modern ''load''.
[ ''Larboard'' sounds similar to ''starboard'' and in 1844 the Royal Navy ordered that ''port'' be used instead.] The United States Navy followed suit in 1846. ''Larboard'' continued to be used well into the 1850s by whalers. In chapter 12 of ''Life on the Mississippi'' (1883) Mark Twain writes ''larboard'' was used to refer to the left side of the ship (Mississippi River steamboat) in his days on the river – circa 1857–1861. Lewis Carroll rhymed ''larboard'' and ''starboard'' in "Fit the Second" of '' The Hunting of the Snark'' (1876).
An Anglo-Saxon record of a voyage by Ohthere of Hålogaland used the word "bæcbord" ("back-board") for the left side of a ship. With the steering rudder on the starboard side the man on the rudder had his back to the bagbord (Nordic for portside) side of the ship. The words for "port side" in other European languages, such as German ''Backbord'', Dutch and Afrikaans ''bakboord'', Swedish ''babord'', Spanish ''babor'', Portuguese '' bombordo'', Italian ''babordo'', French ''bâbord'' and Estonian ''pakpoord'', are derived from the same root.
Importance of standard terms
The navigational treaty convention, the International Regulations for Preventing Collisions at Sea
The International Regulations for Preventing Collisions at Sea 1972 (COLREGs) are published by the International Maritime Organization (IMO) and set out, among other things, the "rules of the road" or navigation rules to be followed by ships a ...
—for instance, as appears in the UK's Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations 1996 (and comparable US documents from the US Coast Guard)—sets forth requirements for maritime vessels to avoid collisions, whether by sail or powered, and whether a vessel is overtaking, approaching head-on, or crossing.[ To set forth these navigational rules, the terms starboard and port are essential, and to aid in '' in situ'' decision-making, the two sides of each vessel are marked, dusk to dawn, by navigation lights, the vessel's starboard side by green and its port side by red.][ Aircraft are lit in the same way.
]
See also
* Anatomical terms of location, another example of terms of directionality that do not depend on the location of the observer for things that are bilaterally symmetrical
* Dexter and sinister
''Dexter'' and ''sinister'' are terms used in heraldry to refer to specific locations in an escutcheon bearing a coat of arms, and to the other elements of an achievement. ''Dexter'' (Latin for 'right') indicates the right-hand side of the sh ...
* Direction (disambiguation)
Direction may refer to:
*Relative direction, for instance left, right, forward, backwards, up, and down
** Anatomical terms of location for those used in anatomy
** List of ship directions
* Cardinal direction
Mathematics and science
*Directio ...
* Glossary of nautical terms
* Handedness
In human biology, handedness is an individual's preferential use of one hand, known as the dominant hand, due to it being stronger, faster or more Fine motor skill, dextrous. The other hand, comparatively often the weaker, less dextrous or sim ...
* Laterality
* Proper right and proper left
* Reflection symmetry
* Sinistral and dextral
Notes
References
{{Aircraft components, state=collapsed
Aeronautics
Nautical terminology
Orientation (geometry)