afstand

Afstand is a measure of the separation between two points or objects. In everyday usage it refers to spatial distance—the length of the path or straight-line gap between locations—or to more abstract notions such as travel distance. In physics and mathematics, distance is a metric: a function that assigns a nonnegative real number to each pair of points, is symmetric, and satisfies the triangle inequality.

The SI base unit for distance is the metre (m). Larger distances are commonly expressed in kilometres (km) or miles. For very large scales, such as those encountered in astronomy, one uses light-years or parsecs. Tools for measuring distance range from rulers and tape measures for small scales to GPS devices and odometers for longer distances, and to map scales that convert real distances on a chart to their drawn representation.

In geometry, the distance between two points in Euclidean space is given by the Pythagorean formula: in two dimensions, distance = sqrt(dx^2 + dy^2); in three dimensions, distance = sqrt(dx^2 + dy^2 + dz^2). More generally, distance can be defined by a metric in any space, which determines how far apart points are.

On the surface of a sphere, such as Earth, distance is typically measured along the surface (great-circle distance) rather than through the interior. The haversine formula is a common method to estimate great-circle distance from latitude and longitude coordinates.

Distance can also be contrasted with displacement: distance is a scalar representing how much ground is covered, whereas displacement is a vector indicating the straight-line difference between start and end points.

Applications include navigation, surveying, logistics, transportation planning, sports analytics, and astronomy. Social or temporal uses of the word distance describe separation in relationships or time, though these are figurative extensions of the physical concept.