# Types of entities

There are 3 different types of entities in the system:

* **Synonyms**: This is the most common type of entities. For each of the main values that the parameter can have, we can detail a list of synonyms that correspond to it, in this way when any of the values declared as synonyms is detected, the main value will be sent.
* **List**: This is the simplest type of entities, it allows you to define a list of main values, but it does not allow you to add synonyms for each one.
* **Regular expressions**: It is the most complex type of entities that can be created, it allows you to define a list of regular expressions whose function is to detect text fragments that comply with an established format, for example: telephone numbers, ID numbers, account numbers. [Learn more about regular expressions](https://www.adictosaltrabajo.com/2015/01/29/regexsam/).