Deposits (and their opposite, loans) are non-negotiable, cash money market instruments in which a sum of money is borrowed - the proceeds - for an agreed period of time - the term to maturity - and on which the borrower pays the lender a pre-arranged amount of income (interest) together with the return of money lent - the principal - at maturity. A deposit is a liability for the borrower and an asset for the lender. Deposits and loans are the main instruments of the interbank market (interbank deposits and loans), where commercial banks make day-to-day adjustments in their operational reserves (liquidity management), offering a fine return on liquid funds. To finance its lending and investment operations, a commercial bank draws funds from various sources. Their base source comprises demand and time deposits. Demand deposits are so called because the depositor can withdraw funds without notice.