A classification system is a means of organising lists of items in a structured and useful way.
There is no single "right" way to classify items, and more than one useful classification system for any list of items is possible. However, some systems may be better, or more useful than others for a given purpose.
Additionally, classification systems sometimes change their definitions. A recent very public and controversial change was the system for classifying bodies in the Solar system. Under the old classification system, Pluto was classified as a "planet", but under the new classification system, its classification was changed to "dwarf planet".
Biblical skeptics frequently attempt to find fault with the Bible which refers, for example, to bats as birds, among a number of similar apparently-incorrect descriptions. However, the writers of the Bible were simply using a different classification system (e.g. a bird is a flying creature) than modern science, which defines birds as creatures with feathers.
Some well-known classification systems are:
- Linnaean taxonomy, for classifying living things.
- Dewey Decimal Classification, for classifying non-fiction books.
- International Astronomical Union, IAU 2006 General Assembly: Result of the IAU Resolution votes Resolutions