What is the Dichotomous Key and how to use it

A dichotomous key is a classification method used to group or identify objects or organisms based on a series of choices that divide them into two mutually exclusive groups. This method is similar to the process of following the branches in a decision tree.

What’s that

A dichotomous key is a tool or method of identifying organisms or objects by comparing their characteristics and making decisions based on the available options. The dichotomy key works by separating objects into two groups based on certain characteristics until the objects are clearly identified.

Here are some important points about the dichotomy key:

  1. A dichotomous key consists of a series of statements or questions that divide objects or organisms into two groups based on certain characteristics or traits.
  2. Each choice in the dichotomous key must be mutually exclusive, meaning only one choice is correct for each statement or question.
  3. By following the branches of the dichotomous key, we can arrive at the final classification or identification of the object or organism.
  4. Examples of the use of dichotomous keys can be found in various fields, such as biology to identify plant or animal species, botany to classify types of plants, or chemistry to differentiate compounds based on their properties.
  5. It is important to look at each statement or question on the dichotomous key carefully and choose the option that best fits the observed characteristics.

In practice, the dichotomous key is often used in taxonomic studies and organism identification. This method helps in obtaining systematic and structured information about various objects or organisms.

How to use

Here are the general steps for using a dichotomous key:

  1. Determining Initial Choices:

Identify the organism or object you want to recognize. These initial choices are usually general questions or statements aimed at large groups.

  1. Following Statements or Choices:

Read the statements or choices given in the dichotomous key. Select the option that best suits the characteristics of the object you identified.

  1. Proceeding to the Next Branch:

After selecting the first option, move on to the next branch of the dichotomous key. Typically, subsequent branches will present further questions or statements that narrow the group of objects based on additional characteristics.

  1. Performing Repeated Elections:

Keep selecting options or following key branches until you reach the end of the identification process. Ultimately, you should arrive at a specific name or category that identifies the organism or object.

  1. Verifying Identification:

After arriving at the final result, ensure that your identification matches the characteristics of the observed object. Double-check all choices and ensure that the choices you make are consistent with the observed characteristics.


A simple example of a dichotomous key:

  1. A. Has flowers –> 2
  2. Does not have flowers –> 3


  1. A. Red flowers –> Roses
  2. White flowers –> Lily


  1. A. Has wide leaves –> Oak
  2. Has narrow leaves –> Pine

In this example, each option provides a distinction between two groups and guides the user to reach the final identification. It is important to read each statement carefully and choose the option that best fits the characteristics of the object you identified.