Final answer:
A 'description' is not an entity; it is rather an explanation or representation of an entity that requires the existence of other entities to be meaningful.
Step-by-step explanation:
The question "Which of the following is not an entity?" pertains to the categorization of items or concepts by their nature. An entity is typically defined as an object or concept that exists either physically or legally and can be distinctly identified. Therefore, a person, an event, and a thing can all be considered entities as they can exist in a tangible or legally recognized form. However, a description in itself is not an entity, it is an account or representation of an entity. A description refers to the words or phrases used to explain or detail something; it does not have a concrete existence or legal status on its own but relies on the existence of other entities.