Interest is popularly thought of as a payment made for the use of money. Commonly, however, the person who borrows money desires to use not the money but something which he buys with it. The borrower, therefore, pays interest for the things for which he exchanges the money rather than for the money itself. In ordinary business procedure interest is paid for the use of productive capital, but it also often happens that the things which the borrower secures with the money or the purchasing power which the lender furnishes him are not productive capital. They may be, for instance, goods ready for consumption. But while they are not productive capital, from the point of view of the lender who has given the borrower control over them they are a source of income and are acquisitive capital. Interest, then, is the remuneration which is paid for the use of capital. The economist uses the term interest to include also the reward which the owner of productive capital receives for it when he uses it productively in his own business. There is some confusion in the popular use of the terms rent and interest. For example, it is usual to speak of the rent of a house and of interest on an investment in land. We shall find it useful to distinguish between the incomes from capital and from land and to refer to the one as interest and to the other as rent. The payment for the use of a house, therefore, is interest and the return for the use of the land upon which the house is located is rent. While both returns are made in one payment they are, economically speaking, distinct incomes.