What are are dichotomous keys?

Dichotomous keys are tools common in Biology used to classify organisms where there are only two options -- the organism either possesses a particular trait or feature or it does not (Moulton, 2004, p. 109). The answer to this question is then used to help biologists and tell them which questions to ask next until all traits have been have been included and investigated (Moulton, 2004, p. 109).

Moulton, Glen E. (2004) The Complete Idiot's Guide to Biology. New York, NY: Alpha Books.