Connected graph without a cycle.

Using trees as a form of representation makes it possible to illustrate the process of counting cases that result in a specific study, such as counting and representing prime factors d’un nombre naturel, of a whole number, counting the possible outcomes of a random experiment, or representing the probabilities associated with one of these results.

### Examples

- We want to create flags with three vertical stripes using four colours so that no two adjoining stripes are the same colour. Here is a tree that illustrates the different possible results:

- This graph illustrates different paths that can be taken to explore a park. This graph is not a tree because it has cycles.