| A | Geothermal | Partially molten | Primarily hydrogen compounds | Gothos |
| B | Geomorteus | Partially molten, high suface temperature | Extremely tenuous, few chemically active gases | Mercury |
| C | Geoinactive | Low surface temperature | Frozen | Pluto, Psi 2000 |
| D | Asteroid/Moon | Barren and cratered | None or very tenuous | Moon (Sol IIIa), Lunar V (Bajor VIIe), Rura Penthe |
| E | Geoplastic | molten, high surface temperature | Hydrogen compounds and reactive gases | Excalibia |
| F | Geometallic | Volcanic eruptions due to molten core | Hydrogen compounds | Janus IV |
| G | Geocrystalline | Still crystalizing | Carbon dioxide, some toxic gases | Delta Vega |
| H | Desert | Hot and arid, little or no surface water | May contain heavy gases and metal vapors | Ocampa, Rigel XII, Tau Cygna V |
| I | Gas Supergiant | Tenuous, comprised of gaseous hydrogen and hydrogen compounds; radiates heat | Zones vary in temperature, pressure and composition; water vapor may be present | Q'tahL |
| J | Gas Giant | Tenuous, comprised of gaseous hydrogen and hydrogen compounds; radiates heat | Zones vary in temperature, pressure and composition | Jupiter, Saturn |
| K | Adaptable | Barren, little or no surface water | Thin, mostly carbon dioxide | Mars, Mudd, Son'a |
| L | Marginal | Rocky and barren, little surface water | Oxygen/argon, high concentration of carbon dioxide | Borg Prime, Indri VIII, Vaadwaur |
| M (Minshara) | Terrestrial | Surface water abundant, covering less than 80% of surface | Nitrogen, oxygen, trace elements | Bajor, Baku, Betazed, Capella, Cardassia Prime, Delta, Earth, Ferenginar, Karemma, Qo' noS, Risa, Romulus, Talax, Tellar Prime, Trill, Vulcan |
| N | Reducing | High surface temperature due to greenhouse effect; water exists only as vapor | Extremely dense, carbon dioxide and sulfides | Venus |
| O | Pelagic | Liquid water covers 80% or more of surface | Nitrogen, oxygen, trace elements | Argo, Pacifica |
| P | Glaciated | Water ice covers 80% or more of surface area | Nitrogen, oxygen, trace elements | Andoria, Breen, Exo III, Rigel X |
| Q | Variable | Ranges from molten to water and/or carbon dioxide ice, due to eccentric orbit or variable output of star | Ranges from tenuous to very dense | Genesis Planet, Remus |
| R | Rouge | May be temperate due to geothermal venting | Primarily volcanic outgassing | Dakala, Founder Homeworld |
| S | Ultragiant (10-50 million km. diameter) | Tenuous, composed of gaseous hydrogen and hydrogen compounds; radiates considerablr heat | Zones vary in temperature, pressure and composition; water vapor may be present | Unknown |
| T | Ultragiant (50-100 million km. diameter) | Tenuous, composed of gaseous hydrogen and hydrogen compounds; radiates considerablr heat | Zones vary in temperature, pressure and composition; water vapor may be present | Unknown |
| Y | Demon | Temperature can exceed 500° K | Turbulent, saturated with toxic chemicals and thermionic radiation | Memetic Homeworld, Tholia |