The dichotomous key is a device used to determine an organism. The word dichotomous is derived from Greek and means something that can be divided into two parts. When dichotomous keys are used a flow chart can be constructed with two paths starting from each node. For example, to identify a plant the following keys would be dichotomous: the leaves of the plant are serrated, the adult plant is a large tree, the leaves change color in autumn, the plant produces seed, etc.
All keys do not have to be dichotomous. Questions that can have more than two answers can easily be created; for example, what color are the flowers of the plant, how are the seed of the plant dispersed, etc.
The use of dichotomous keys makes the process of identification simpler.