Cardinal directions are defined as one of the four main points on a compass in the direction of north, south, east and west. These directions are commonly denoted by their initials: N, S, E, and W.
A compass also contains intermediate or intercardinal directions in between each cardinal point that include northeast (NE), southeast (SE), southwest (SW) and northwest (NW). Additionally, the intermediate direction of every set of intercardinal and cardinal direction is called a secondary-intercardinal direction, which include NNE, ENE, ESE and so on.
A magnetic compass uses the Earth's magnetic field to determine the cardinal directions. The Earth's magnetic field is approximately aligned with its axis, making the use of this tool possible. Magnetic compasses are very widely used, but only moderately accurate.
First invented as a device for divination, the magnetic compass was used as early as the Chinese Han Dynasty and later adopted for navigation by the Song Dynasty Chinese during the 11th century. The use of a compass is recorded in Western Europe and in Persia around the early 13th century. The first compasses in Han Dynasty China were made of lodestone, a naturally magnetized ore of iron. Later compasses were made of iron needles, magnetized by striking them with a lodestone. Today, most compasses are magnetic and liquid filled.