Dichotomous key

A dichotomous key is a method used to help people identify an organism. The key is broken up into a series of questions and these questions are arranged in pairs. Depending on the answer to the question the person using the key progresses from question to question until they have identified the organism.

An example key to separate out different shapes (square, rectangle, triangle, pentagon, hexagon) might be:

  1. Shape has 4 sides or less -> Go to 2
    Shape has 5 sides or more -> Go to 4
  2. Shape has three sides -> Shape is a triangle
    Shape has four sides -> Go to 3
  3. Shape has four sides of equal length -> Shape is a square
    Shape does not have four sides of equal length -> Shape is a rectangle
  4. Shape has five sides -> Shape is a pentagon
    Shape has six sides -> Shape is a hexagon

Other names for (or types of) Dichotomous key include:

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