In
mathematics, the
capacity of a set in
Euclidean space is a measure of that set's "size". Unlike, say,
Lebesgue measure, which measures a set's
volume or physical extent, capacity is a mathematical analogue of a set's ability to hold
electrical charge. More precisely, it is the
capacitance of the set: the total charge a set can hold while maintaining a given
potential energy. The potential energy is computed with respect to an idealized ground at infinity for the
harmonic or
Newtonian capacity, and with respect to a surface for the
condenser capacity.