The Soybean (U.S.) or Soya bean (UK) is a species of legume, native to eastern Asia. It is an annual plant, which may vary in growth habit and height. It may grow prostrate, not growing above 20 cm (7.8 inches); up to stiffly erect plants growing to 2 meters (6.5 feet).

The pods, stems, and leaves are covered with fine brown or gray pubescence. The leaves are trifoliate (sometimes with 5 leaflets), the leaflets 6-15 cm (2-6 inches) long and 2-7 cm (1-3 inches) broad; they fall before the seeds are mature. The small, inconspicuous, self-fertile flowers are borne in the axil of the leaf and are either white or purple; The fruit is a hairy pod that grow in clusters of 3-5, with each pod 3-8 cm (1-3 inches) long and usually containing 2-4 (rarely more) seeds 5-11 mm in diameter.

Like corn and some other crops of long domestication, the relationship of the modern soybean to wild-growing species can no longer be traced with any degree of certainty. It is a cultural variety (a cultigen) with a very large number of cultivars. However, it is known that the progenitor of the modern soybean was a vine-like plant, that grew prone on the ground.

Beans are classed as pulses whereas soybeans are classed as oilseeds. The word soy is derived from the Japanese word shoyu (soy sauce/soya sauce).

Cite: Wikipedia