A capital requirement (also known as regulatory capital, capital adequacy or capital base) is the amount of capital a bank or other financial institution has to have as required by its financial regulator. This is usually expressed as a capital adequacy ratio of equity as a percentage of risk-weighted assets. These requirements are put into place to ensure that these institutions do not take on excess leverage and risk becoming insolvent. Capital requirements govern the ratio of equity to debt, recorded on the liabilities and equity side of a firm's balance sheet. They should not be confused with reserve requirements, which govern the assets side of a bank's balance sheet—in particular, the proportion of its assets it must hold in cash or highly-liquid assets. Capital is a source of funds not a use of funds.