The definition of a bean is the edible seed of various plants.
Chickpeas, lentils and limas are each an example of a bean.
See bean in Webster's New World College Dictionary
Origin: ME ben < OE bean; akin to ON baun, Ger bohne < ? IE *bhabhā > L faba, bean
See bean in American Heritage Dictionary 4
Origin: Middle English ben, broad bean
Origin: , from Old English bēan; see bha-bhā- in Indo-European roots.
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