temporary market where buyers and sellers gather to transact business. A fair is held at regular intervals, generally at the same location and time of year, and it usually lasts for several days or even weeks. Its primary function is the promotion of trade. Historically, fairs displayed many different kinds of products in specific commodity or industrial groupings. The older specialty fair evolved into the more modern trade show. Participation in contemporary trade shows is confined to exhibitors representing one industry or even just specialized segments of an industry.

Historically, fairs were created to solve the early problems of distribution. They provided an opportunity for the demonstration of skills and crafts, for the exchange of ideas, and for the bartering of goods. They concentrated supply and demand in certain places at certain times. Fairs were a fixture of the Roman Empire (ancient Rome), and the Romans introduced markets and fairs into northern Europe to encourage trade within their conquered provinces. When the Western Roman Empire disintegrated in the late 5th century, virtually all organized commerce in Europe ceased until the late 7th century. Trade revived under Charlemagne, and fairs eventually evolved from some of the local markets, particularly at points of major caravan route intersections and wherever people congregated for religious festivals. The methods of commerce introduced at such fairs became widespread, and the rules of the fair eventually became the basis of European business law.

The largest of the fairs became quite important. The fair at Saint-Denis near Paris had already risen to prominence in the 7th century, and the Easter fairs at Cologne (Germany) were equally popular in the 11th century. From the mid-12th century on for several hundred years, the fairs of Champagne (France) reigned supreme among the important fairs of Europe. Products from throughout Europe and beyond, including furs from Russia, drugs and spices from East Asia, cloth from Flanders, and linens from southern Germany, were traded there. Important fairs also arose at Lyon (France), Geneva, and Stourbridge (England). Among other fairs of historical interest were those at Kinsai in China, which flourished during Europe's Dark Ages; the great Aztec fair that the Spanish conquistadores found on the present-day site of Mexico City; and the Nizhny Novgorod fair in central Russia. These fairs all succeeded because they were located on major trade or pilgrimage routes.

In almost every civilization—as commerce became standardized, transportation was organized, and cities grew large enough to require daily markets—fairs have become less important. Sometimes they evolved into religious festivals or sites for recreation and amusement. Others were ruined by excessive taxation of greedy rulers, and still others, particularly in modern times, have simply been suppressed; the Soviet Union (Union of Soviet Socialist Republics) abolished all of its 17,500 fairs in 1930 as being “unsuited to the Soviet economic and political objective.” The commerce of western Europe during the feudal era was largely based on fairs, but, with the coming of the Industrial Revolution, the vitality of the great fairs was sapped; many perished, and the character of many others changed. One remaining vestige of such fairs is found in the county, agricultural, and livestock fairs that are still popular in the United States and in Europe.