Kilometre
A kilometre is a metric unit of length equal to 1,000 metres. It is commonly used to measure distances between places and along routes.
Metre: The SI base unit of length, defined by fixing the speed of light in vacuum. A kilometre is exactly 1,000 metres.
Road distance: The length of a route measured along a road network. Road signs and route descriptions commonly state distances in kilometres.
Nautical mile: A unit of distance equal to 1,852 metres, used chiefly in navigation and aviation. It is a distinct navigation unit, not another name for a kilometre.
Metric system: A decimal system of measurement based on units such as the metre and gram. The kilometre is one of its length units, formed using a decimal prefix.
Metric prefix: A word or symbol attached to a unit to indicate a decimal multiple or fraction. The prefix kilo- marks a factor of 1,000 in kilometre.
Kilometre marker: A roadside marker indicating a location's distance along a route, often from a defined starting point. Markers use kilometres to locate positions and measure progress along roads.
Square kilometre: A unit of area equal to the area of a square with sides one kilometre long. The added square changes a length unit into an area unit.
French Revolution: A period of political and social upheaval in France beginning in 1789. Revolutionary France initiated the project that established the metric system.
International System of Units: The internationally standardized system of measurement built around seven base units. The metre, and thus the kilometre, belongs to this system.
Geodesy: The science of measuring Earth's shape, orientation, and gravitational field. Geodesy uses kilometres to describe large terrestrial distances.