Which type of bean is not actually a bean?

Castor “beans” are botanically classified as seeds and are not typically considered food. Processing castor oil from castor-plant seeds removes the toxic compound, ricin.

Castor beans contain ricin, for which there is no known antidote. It has been used in actual murders and failed murder attempts and, famously, in the AMC television series, “Breaking Bad.” Although it does not kill immediately, it can be delivered as a mist, powder, pellet, or dissolved in water or a slightly-acidic liquid. Depending on body weight, eating as few as three or four castor beans can be fatal.

Actual beans, such as kidney, lima, garbanzo, and fava, are entirely safe when handled properly. Raw or dried beans need to be cooked in rapidly boiling water for 10 minutes. Canned beans have been cooked and are assumed to have been properly processed.