Categorical variables

“Categorical variables are measures that can take on two or more categories, which may be
Unordered categories: such as a person’s country of origin, the colour of a car, or the hospital in which an operation takes place.
Ordered categories: such as the rank of military personnel.
Numbers that have been grouped: such as levels of obesity, which is often defined in terms of thresholds for the body mass index (BMI).”

Excerpt From: David Spiegelhalter. “The Art of Statistics: Learning From Data (Pelican Books).”