Usury (/ˈjuːʒəri/) is, as defined today, the practice of making unethical or immoral monetary loans that unfairly enrich the lender. Originally, usury meant interest of any kind. A loan may be considered usurious because of excessive or abusive interest rates or other factors. Historically in Christian societies, and still in many Islamic societies today, charging any interest at all can be considered usury. Someone who practices usury can be called a usurer, but a more common term in contemporary English is loan shark.
The term may be used in a moral sense—condemning, taking advantage of others' misfortunes—or in a legal sense where interest rates may be regulated by law. Historically, some cultures (e.g., Christianity in much of Medieval Europe, and Islam in many parts of the world today) have regarded charging any interest for loans as sinful.
Some of the earliest known condemnations of usury come from the Vedic texts of India. Similar condemnations are found in religious texts from Buddhism, Judaism, Christianity, and Islam (the term is riba in Arabic and ribbit in Hebrew). At times, many nations from ancient China to ancient Greece to ancient Rome have outlawed loans with any interest. Though the Roman Empire eventually allowed loans with carefully restricted interest rates, the Christian church in medieval Europe banned the charging of interest at any rate (as well as charging a fee for the use of money, such as at a bureau de change).
Public speaker Charles Eisenstein has argued that the pivotal change in the English-speaking world seems to have come with lawful rights to charge interest on lent money, particularly the 1545 Act, "An Act Against Usurie" (37 H. viii 9) of King Henry VIII of England.