Gradian

A gradian is an angular unit equal to one-hundredth of a right angle, or one four-hundredth of a full turn. It is also called a gon.

Angle: A geometric measure of the rotation between two rays sharing an endpoint. A gradian is one unit used to measure angles.
Degree–gradian conversion: The numerical relationship between angle measures expressed in degrees and gradians. A degree equals 10/9 of a gradian, enabling direct conversion.
French Revolutionary units of measurement: Units promoted in revolutionary France to organize measurement around decimal divisions. The gradian belongs to the same decimal reforming impulse.
Land surveying: The measurement of land features and boundaries for mapping and property definition. Some surveying traditions use 400-part circle divisions for bearings and angles.
Right angle: An angle of 90 degrees, formed by perpendicular lines or rays. One right angle is exactly 100 gradians.
Decimal angle measurement: The representation of angles in a positional decimal unit system. Each gradian divides into decimal fractions rather than minutes and seconds.
Metric system: A decimal system of measurement standardized around units such as the metre and kilogram. Gradians extend decimal subdivision to angles, though they are not a standard SI unit.
Theodolite: An optical instrument that measures horizontal and vertical angles. Some theodolites provide gradian graduations for field measurements.
Full turn: A rotation that returns a direction to its starting orientation. One complete rotation contains exactly 400 gradians.
Surveying: The measurement and mapping of land, boundaries, and spatial positions. Surveying instruments and calculations have used 400-part circle scales.

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