By convention, the top side of a map is often north.
- North is used (explicitly or implicitly) to define all other directions.
- The (visual) top edges of maps usually correspond to the northern edge of the area represented, unless explicitly stated otherwise or landmarks are considered more useful for that territory than specific directions.
- On any rotating object, north denotes the side appearing to rotate counter-clockwise when viewed from afar along the axis of rotation.
The word north is related to the Old High German nord, both descending from the Proto-Indo-European unit ner-, meaning "down" (or "under"). (Presumably a natural primitive description of its concept is "to the left of the rising sun".)
Latin borealis is from Greek boreas "north wind, north", in mythology (according to Ovid) personified as the son of the river-god Strymon, and father of Calais and Zetes; septentrionalis is from septentriones, "the seven plow oxen", a name of Ursa Maior. Greek arktikos "northern" is named for the same constellation (cf. Arctic).
Other languages have sometimes more interesting derivations. For example, in Lezgian kefer can mean both 'disbelief' and 'north', since north of Muslim Lezgians there are areas inhabited by non-Muslim (until recently) Caucasian peoples, such as Avars and Chechens; as well as pagan Turkic peoples. In many languages of Mesoamerica, 'north' also means 'up'. In Hungarian the word for North is "észak" which is derived from "éjszaka" (night) as on the Northern Hemisphere the Sun never shines from North, therefore it's a realm of night.
Magnetic north and declination
Magnetic north is of interest because it is the direction indicated as north on a properly functioning (but uncorrected) magnetic compass. The difference between it and true north is called the magnetic declination (or simply the declination where the context is clear). For many purposes and physical circumstances, the error in direction that results from ignoring the distinction is tolerable; in others a mental or instrument compensation, based on assumed knowledge of the applicable declination, can solve all the problems. But simple generalizations on the subject should be treated as unsound, and as likely to reflect popular misconceptions about terrestrial magnetism.
Maps intended for usage in orienteering by compass will clearly indicate the local declination for easy correction to true north. Maps may also indicate grid north, which is a navigational term referring to the direction northwards along the grid lines of a map projection.
The visible rotation of the night sky around the visible celestial pole provides a vivid metaphor of that direction corresponding to up. Thus the choice of the north as corresponding to up in the northern hemisphere, or of south in that role in the southern, is, prior to world-wide communication, anything but an arbitrary one. On the contrary, it is of interest that Chinese and Islamic culture even considered south as the proper top end for maps.
In Western culture:
- Maps tend to be drawn for viewing with either true north or magnetic north at the top
- Globes of the earth have the North Pole at the top, or if the Earth's axis is represented as inclined from vertical (normally by the angle it has relative to the axis of the Earth's orbit), in the top half.
- Maps are usually labelled to indicate which direction on the map corresponds to a direction on the earth* usually with a single arrow oriented to the map's representation of true north,
- occasionally with a single arrow oriented to the map's representation of magnetic north, or two arrows oriented to true and magnetic north respectively,
- occasionally with a compass rose, but if so, usually on a map with north at the top and usually with north decorated more prominently than any other compass point.
- Up is a metaphor for north. The notion that north should always be up and east at the right was established by the Greek astronomer Ptolemy. The historian Daniel Boorstin suggests that perhaps this was because the better-known places in his world were in the northern hemisphere, and on a flat map these were most convenient for study if they were in the upper right-hand corner.
Roles of east and west as inherently subsidiary directions
While the choice of north over south as prime direction reflects quite arbitrary historical factors, east and west are not nearly as natural alternatives as first glance might suggest. Their folk definitions are, respectively, "where the sun rises" and "where it sets". Except on the Equator, however, these definitions, taken together, would imply that
- east and west would not be 180 degrees apart, but instead would differ from that by up to twice the degrees of latitude of the location in question, and
- they would each move slightly from day to day and, in the temperate zones, markedly over the course of the year.
Reasonably accurate folk astronomy, such as is usually attributed to Stone Age peoples or later Celts, would arrive at east and west by noting the directions of rising and setting (preferably more than once each) and choosing as prime direction one of the two mutually opposite directions that lie halfway between those two. The true folk-astronomical definitions of east and west are "the directions, a right angle from the prime direction, that are closest to the rising and setting, respectively, of the sun (or moon).
- The phrase "north of X" is often used to mean "more than X" or "greater than X", i.e. "The world population is north of 7 billion people" or "north of 40 [years old]".