Definition: A hectare (ha) is a non-SI metric unit of area equal to 10,000 square meters. It is primarily used for measuring land area.

History/origin: The hectare was adopted as a unit of area following the French Revolution, along with the metric system. It is derived from the word 'hecto,' meaning one hundred, and 'are,' which is a unit of area equal to 100 square meters.

Current use: Hectares are commonly used in agriculture, forestry, land management, and urban planning to measure large areas of land. It's a widely used unit in many countries, particularly for agricultural land.