A hectare (symbol ha, pronounce /ˈhɛktɛər/) is a unit of area equal to 10,000 square metres, or one square hectometre, and commonly used for measuring land area. A 100 m square is one ha. Its base unit, the are, was defined by older forms of the metric system, but is no longer part of the modern metric system. The Comité International des Poids et Mesures classifies the hectare as a unit that is accepted for use with SI.