What is a taxonomy?

Rating A taxonomy is a way of classifying things. For example, in the US, movies are rated as G, PG, PG-13, R, or NC-17. Classifying movies helps people make decisions about what they want to see.

Some taxonomies are closed, that is, the number of items is fixed, and rarely, if ever, changes. The movie ratings are like that. The categories haven’t changed in years.

Other taxonomies are open, meaning that new categories are added from time to time. Take Amazon, for example.