Speed at which a chemical reaction proceeds, in terms of amount of product formed or amount of reactant consumed per unit of time. The reaction rate depends on the nature of the reacting substances and the type of chemical change, as well as temperature and pressure, especially if gases are involved. In general, the reactions of ions occur very rapidly, but those in which covalent bonds are formed or broken are slower. Catalysts usually accelerate reaction rates. The prediction, measurement, and interpretation of reaction rates are subjects of the branch of chemistry known as chemical kinetics. Seealso mass action, law of.
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Price of one country's money in relation to another's. Exchange rates may be fixed or flexible. An exchange rate is fixed when two countries agree to maintain a fixed rate through the use of monetary policy. Historically, the most famous fixed exchange-rate system was the gold standard; in the late 1850s, one ounce of gold was defined as being worth 20 U.S dollars and 4 pounds sterling, resulting in an exchange rate of 5 dollars per pound. An exchange rate is flexible, or “floating,” when two countries agree to let international market forces determine the rate through supply and demand. The rate will fluctuate with a country's exports and imports. Most world trade currently takes place with flexible exchange rates that fluctuate within relatively fixed limits. Seealso exchange control, foreign exchange.
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Interest rate charged by a central bank for loans of reserve funds to commercial banks and other financial intermediaries. The discount rate is one important indicator of the condition of monetary policy in an economy. Because raising or lowering the discount rate alters the rates that commercial banks charge on loans, adjustment of the discount rate is used as a tool to combat recession and inflation.
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This designation became especially common because it included the 74-gun ship, which eventually came to be the most popular size of large ship for navies of several different nations. It was an easier ship to handle than a first or second rate ship, but still possessed enough firepower to potentially destroy any single opponent. It was also cheaper to operate.
Although the rating system was only used by the Royal Navy, British authors might still use "third-rate" to speak of a French 74. By the end of the 18th century, the rating system had mostly fallen out of common use, ships of the line usually being characterized directly by their number of guns, the numbers even being used as the name of the type, as in "a squadron of three 74s".