Taxonomy is a noun that refers to a system of classification. 

Our word of the day comes from the Greek word taxis (TAK sees) which means ‘arrangement’ along with the Greek suffix N-O-M-A-N-I-A, which means ‘distribution.’ Taxonomy emerged in the early 19th century and is mostly used in reference to classifying organisms. Here’s an example:

It’s a good thing the people who discovered this cave were skilled at taxonomy. Otherwise, nerds like me would never know what kind of creatures existed here centuries ago.