combine, agricultural machine that performs both harvesting and threshing operations. Although it was not widely used until the 1930s, the combine was in existence as early as 1830. Early combines were traction-powered and drawn by horses, or later, driven by steam and internal-combustion engines. Self-propelled units appeared in the 1940s and have been adopted worldwide. Modern units feature dust-free, air-conditioned cabs and can handle more than 100 acres (41 hectares) of grain per day. Originally developed for cereal grains, the combine has been adapted to legumes, forage grasses, sorghum, and corn. The basic operations of a combine include cutting and gathering the standing crop, threshing the seed from the stem, separating the chaff, collecting the seed in a hopper for delivery to a truck, and returning the straw to the ground. The combine has replaced the reaper; the binder, which cut and bound a harvested crop into bundles ready for threshing; and the thresher.

Farm machine used, mainly in developed countries, to harvest wheat and often other cereals. The mechanical ancestor of today's large combines was Cyrus H. McCormick's reaper, introduced in 1831. Threshing machines were powered first by men or animals, often using treadmills, later by steam engines and internal-combustion engines. The modern combine harvester, originally introduced in California circa 1875, came into wide use in the U.S. in the 1920s and '30s and in Britain in the 1940s. The self-propelled combine was introduced in 1940. The combine cuts the standing grain, threshes out the grain from the straw and chaff, cleans the grain, and empties it into bags or grain-storage facilities. It has greatly reduced harvesting time and labour; whereas in 1829 harvesting an acre of wheat required 14 man-hours, the modern combine requires less than 30 minutes.

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