Bean originally referred to the seed of the broad or fava bean, but was later expanded
to include members of the New World genus Phaseolus, such as the common bean and the
runner bean, and the related genus Vigna. The term is now applied generally to many
other related plants such as Old World soybeans, peas, chickpeas (garbanzos),
vetches, and lupins.
Bean is sometimes used as a synonym of pulse, an edible legume, though the term
pulses is usually reserved for leguminous crops harvested for their dry grain. The
term bean usually excludes crops used mainly for oil extraction (such as soybeans and
peanuts), as well as those used exclusively for sowing purposes (such as clover and
alfalfa). Leguminous crops harvested green for food, such as snap peas, snow peas, and
so on, are not considered beans, and are classified as vegetable crops. According to
United Nation's Food and Agriculture Organization the term bean should include
only species of Phaseolus; however, a strict consensus definition has proven difficult
because in the past, several species such as Vigna (angularis (azuki bean), mungo (black
gram), radiata (mung bean), aconitifolia (moth bean)) were classified as Phaseolus
and later reclassified. The use of term bean to refer to species other than Phaseolus
thus remains. In some countries, the term bean can mean a host of different species.
In English usage, the word bean is also sometimes used to refer to the seeds or pods
of plants that are not in the family leguminosae, but which bear a superficial resemblance to true beans—for example coffee
beans, castor beans and cocoa beans (which
resemble bean seeds), and vanilla beans, which superficially resemble bean pods.