I created this (unfinished) table for an article about Type Origin I want to be on Bulbapedia. I need to put it somewhere else I think, but I guess it'll be fine here for now:
|Electric||Bioelectrogenetic Animals||Shocking/Charging/Draining Electricity||Electric(ity)/Energy/Static Electricity/Light**||x|
|Steel||Robots/Knights and Other Armored Warriors||Hardening||Metal/Steel||Industry/Artificial Environments|
|Rock||Living or Resurrected Fossils||Polishing/Sculpting||Stone/Rock||x|
|Ice||Polar Animals||Freezing||Ice/Cold||Polar Regions/Frozen Landscapes|
|Psychic||Aliens||Mind Reading/Future Seeing/Mind controlling||ESP(er) (Psychic)/Mind/Spirit/Time/Genetics/Emotions||Space|
|Fire||x||Burning/Heating/Fire Spitting||Fire (Flames)/Magma/Heat||Volcanos|
|Water||Fishes and Other Aquatic Animals||Swimming||Water/Rain||(Under)Water/Sea/Ocean/Rivers|
|Grass||Plants and Mushrooms||Photosynthesizing/Growing||Vegetation/Grass/Wood||Woods/Forests|
|Ghost||Ghosts||Passing Through Objects/Scaring||Death||Graveyards|
|Fairy||Fairies/Magical Beings/Elves/Angels/Cute Beings||x||Life/Love***||x|
|Bug||Insects, Arachnids and Gastropods/Bugs||Leeching||x||x|
- *Sound seems to switch between Normal and Flying.
- **Light seems to switch between Normal and Electric.
- ***Love could become part of Fairy in Generation VI.
- A Pokémon’s type is decided by:
- What for kind of being the Pokémon is (based on).
- What for kind of action the Pokémon (is able to) perform(s).
- What for kind of element the Pokémon (partially) consists of, possesses, represents or contains.
- What for kind of environment the Pokémon lives in, is commonly found in, protects, represents or rules over.
- Sometimes a Pokémon would get more than three types, considering the above list; in that case the two most important features of a Pokémon are taken into consideration. (Charizard; Beedrill) Exceptions are when the balance or expansion of the type combination chart is more in favor. (Stunfisk)
- Sometimes a Pokémon that could easily get two types, considering the above list, only gets the most important or most relevant one. (Glalie; Cofagrigus; Voltorb; Pikachu; Marill; Growlithe) A Pokémon may still obtain the second type upon Mega Evolution. (Ampharos)