Position is the specification of where an object, point, or entity is situated in space or in an ordered system. It answers the question "where?" by relating the thing being described to a chosen reference: an origin, a landmark, a map, or an index. The notion applies at many scales, from the location of a star in the sky to the index of a character in a text string.
Ways to express position
Common methods for recording position include fixed addresses and labels, coordinate systems, and relative descriptions. Coordinate systems assign numbers to positions so they can be manipulated mathematically. Familiar examples are Cartesian coordinates (x, y, z) for flat or three‑dimensional space, polar or cylindrical coordinates for circular symmetry, and geographic latitude/longitude for points on Earth. Addresses, map grid references, and indexes in lists are nonnumeric or mixed systems that also convey position.
Reference frames and relativity
Position is meaningful only relative to a reference frame. The same physical point has different coordinate values if the origin or orientation changes. In physics and engineering this leads to the distinction between absolute and relative position: absolute coordinates use a fixed reference, while relative position expresses where something is compared to another moving or stationary object. Changing frames is a routine mathematical operation involving translation and rotation.
Mathematics and physics
In mathematics a position is often represented by a point in a space and by coordinate tuples. In physics a position is associated with a position vector, usually written r, that points from an agreed origin to the object. Tracking how that vector changes with time describes motion (velocity and acceleration). Precision and uncertainty also matter: measurements always have limits, so reported positions include error bounds or confidence regions.
Applications and examples
- Navigation and mapping: coordinates and map grids locate towns, routes, and natural features.
- Engineering and robotics: precise positions guide manufacturing, assembly, and motion planning.
- Computer science: data structures index positions in arrays or strings; graphical interfaces place elements by coordinates.
- Everyday use: saying "the book is on the table" is a simple relative position description.
Distinctions and notable facts
"Position" differs from related concepts. Location is often used interchangeably but can imply a more concrete address or place, while orientation specifies the direction an object faces rather than where it sits. In cartography and geodesy, the chosen datum and coordinate reference system affect numerical positions: the same physical point can have different coordinate values under different datums. Finally, many disciplines augment position with time, producing spatiotemporal coordinates for moving objects.