# Collection of Scientific and Other Classifications

One might think all we do is stamp-collecting.

* Mathematics
    * [Classification of simple finite groups](https://en.wikipedia.org/wiki/Classification_of_finite_simple_groups)
    * [Classification of manifolds](https://en.wikipedia.org/wiki/Classification_of_manifolds) and [surfaces](https://en.wikipedia.org/wiki/Surface_\(topology\)#Classification_of_closed_surfaces)
        * [Regular polytopes](https://en.wikipedia.org/wiki/Regular_Polytopes)
        * [Elementary cellular automata](https://en.wikipedia.org/wiki/Elementary_cellular_automata)
        * [Symmetry groups](https://en.wikipedia.org/wiki/Symmetry_groups)
            * [Wallpaper groups](https://en.wikipedia.org/wiki/Wallpaper_groups)
            * [Space groups](https://en.wikipedia.org/wiki/Wallpaper_groups)
            * [Bieberbach groups](https://en.wikipedia.org/wiki/Bieberbach_group)
        * [Classification of reversible bit operations](https://arxiv.org/abs/1504.05155)
            * Also [Post's lattice](https://en.wikipedia.org/wiki/Post's_lattice)
        * [Complexity classes](https://en.wikipedia.org/wiki/List_of_complexity_classes) and their relations
            * [Arithmetic hierarchy](https://en.wikipedia.org/wiki/Arithmetic_hierarchy)
            * [Polynomial hierarchy](https://en.wikipedia.org/wiki/Polynomial_hierarchy)
            * [Chomsky hierarchy](https://en.wikipedia.org/wiki/Chomsky_Hierarchy)
        * Stability theory
            * [Poincaré maps](https://en.wikipedia.org/wiki/Poincaré_map) of linear [autonomous systems](https://en.wikipedia.org/wiki/Autonomous_system_\(Mathematics\))
        * Game theory
            * [Classification](https://www.lesswrong.com/s/yiFxBWDXnLpbWGTkK/p/KwbJFexa4MEdhJbs4) of [$2 \times 2$ normal-form games](https://arxiv.org/pdf/1010.4727.pdf)
* Physics
    * [Standard Model](https://en.wikipedia.org/wiki/Stellar_Classification)
        * Classifies all [fundamental particles](https://en.wikipedia.org/wiki/Fundamental_particles)
    * Cosmology
        * [Stellar classification](https://en.wikipedia.org/wiki/Stellar_Classification)
        * [Galaxy classification](https://en.wikipedia.org/wiki/Galaxy_morphological_classification)
        * Orbital mechanics
            * [Lagrange points](https://en.wikipedia.org/wiki/Lagrange_Points)
            * Different types of orbits
* Chemistry
    * [Periodic Table of Elements](https://en.wikipedia.org/wiki/Periodic_Table_of_Elements)
    * [Synthetic polymers](https://en.wikipedia.org/wiki/List_of_synthetic_polymers)
    * [Hazardous materials classification](https://en.wikipedia.org/wiki/Hazardous_materials_labels)
* Biology
    * [Phylogenetic tree of life](https://en.wikipedia.org/wiki/Phylogenetic_Tree)
    * [Linnean taxonomy](https://en.wikipedia.org/wiki/Linnean_taxonomy)
    * [Classification of viruses](https://en.wikipedia.org/wiki/Classification_of_viruses), e.g. the [ICTV classification](https://en.wikipedia.org/wiki/International_Committee_on_Taxonomy_of_Viruses)
    * Various schemes for [biomes](https://en.wikipedia.org/wiki/Biome#Classifications), e.g. the [Holdridge life zones](https://en.wikipedia.org/wiki/Holdridge_Life_Zones)
* Earth science
    * [Geologic time scale](https://en.wikipedia.org/wiki/Geological_timescale)
    * [Cloud genera](https://en.wikipedia.org/wiki/Cloud_genera)
    * Soil classification: [USDA soil taxonomy](https://en.wikipedia.org/wiki/USDA_soil_taxonomy)
    * Classifications of [snow](https://en.wikipedia.org/wiki/Classifications_of_snow) and [snowflakes](https://en.wikipedia.org/wiki/Snowflake#Classification)
    * [Classification of minerals](https://en.wikipedia.org/wiki/Classification_of_minerals), separated beautifully into:
        * [Organic](https://en.wikipedia.org/wiki/Classification_of_organic_minerals)
        * [Silicate](https://en.wikipedia.org/wiki/Classification_of_silicate_minerals)
        * [Non-silicate](https://en.wikipedia.org/wiki/Classification_of_non-silicate_minerals)
    * Also [meteorites](https://en.wikipedia.org/wiki/Classification_of_meteorites)
    * [Trewartha](https://en.wikipedia.org/wiki/Trewartha_climate_classification) and [Köppen](https://en.wikipedia.org/wiki/Köppen_Climate_Classification) climate classifications
* Linguistics
    * [International phonetic alphabet](https://en.wikipedia.org/wiki/International_Phonetic_Alphabet)
    * [Language families](https://en.wikipedia.org/wiki/Language_families), [list](https://en.wikipedia.org/wiki/List_of_language_families)
    * [Unicode](https://en.wikipedia.org/wiki/Unicode)
* Medicine
    * Medical classification: [ICD-10](https://en.wikipedia.org/wiki/ICD-10)
        * Leading to many *many* subclassifications, e.g. of [asthma](https://en.wikipedia.org/wiki/Asthma#Classification), [breast cancer](https://en.wikipedia.org/wiki/Classification_of_breast_cancer), [obesity](https://en.wikipedia.org/wiki/Classification_of_obesity), of course [diabetes](https://en.wikipedia.org/wiki/Diabetes) ([type 1](https://en.wikipedia.org/wiki/Diabetes_Type_1) and [type 2](https://en.wikipedia.org/wiki/Diabetes_type_2)) and [strokes](https://en.wikipedia.org/wiki/Stroke) (ischemic and hemorrhagic)…
    * Psychiatric classification: [DSM-5](https://en.wikipedia.org/wiki/DSM-5)
    * [Blood types](https://en.wikipedia.org/wiki/Blood_Types)
* Psychology
    * [Various proposed classifications of emotions](https://en.wikipedia.org/wiki/Classification_of_emotions)
* Culture
    * Music
        * [Musical genres](https://en.wikipedia.org/wiki/List_of_musical_genres)
        * [Musical instruments](https://en.wikipedia.org/wiki/Classification_of_Instruments), especially [percussion instruments](https://en.wikipedia.org/wiki/Classification_of_percussion_instruments)
    * Food
        * [Wines](https://en.wikipedia.org/wiki/Classification_of_wine)
        * [Champagne](https://en.wikipedia.org/wiki/Classification_of_Champagne)
* Meditation
    * [Jhanas](https://en.wikipedia.org/wiki/Jhāna)
    * [Maps](https://www.integrateddaniel.info/mind-maps) [of insight](https://www.dharmaoverground.org/dharma-wiki/-/wiki/Main/MCTB+The+Progress+of+Insight)
* [Dewey Decimal classification](https://en.wikipedia.org/wiki/Dewey_Decimal_System)

A classification of classifications, if you will.

Sporadic elements include classifications of [cars](https://en.wikipedia.org/wiki/Classification_of_cars), [demons](https://en.wikipedia.org/wiki/Classification_of_demons), [fairies](https://en.wikipedia.org/wiki/Classifications_of_fairies), and [swords](https://en.wikipedia.org/wiki/Classification_of_swords).