Hectare

• abstract: The hectare ( or ; symbol ha) is a metric unit of area defined as 10,000 square metres (100 m by 100 m), and primarily used in the measurement of land. In 1795, when the metric system was introduced, the 'are' was defined as 100 square metres and the hectare ('hecto-' + 'are') was thus 100 'ares' or 1/100 km2.

以上来源于: WordNet