The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- MarineWaveEnergyPowerPlant (0 members)
- WaterBody (2 members)
- InternalCombustionVehicle (4 members)
- SquareCentimeter (0 members)
- DownholeHeatExchanger (0 members)
- CompressedGasCar (0 members)
- CokeOvenGas (0 members)
- ExternalImportOntologyModule (0 members)
- LowerYieldStrength (0 members)
- Micrometer (0 members)
- HouseholdSector (0 members)
- BaseQuantityKind (6 members)
- RealizableEntity (3 members)
- EconomicStockPotential (0 members)
- Volatility (0 members)
- Yard (0 members)
- MassDensityUnit (11 members)
- GasGrid (0 members)
- ElectricMotor (1 member)
- BatteryPassportCePass (1 member)
- AmortisationTime (0 members)
- ReservoirHydroStoragePowerPlant (0 members)
- UnitedStatesCustomaryCup (0 members)
- SteamReforming (0 members)
- InvestmentCost (5 members)
- GridComponentLink (1 member)
- Lux (0 members)
- Curie (0 members)
- Dam (0 members)
- PowerToFuelSystem (2 members)
- EnergyStorageLevel (0 members)
- PotentialEnergyStorageFunction (0 members)
- MarineWaveEnergyConvertingUnit (0 members)
- Microgray (0 members)
- FuelSupplySystem (0 members)
- PropertyCost (0 members)
- UtilisationValue (2 members)
- Subregion (1 member)
- Surface (1 member)
- 2DPixelCoordinates (2 members)
- FinalEnergyCarrierDisposition (0 members)
- DegreeFahrenheit (0 members)
- OpticalMicroscopy (1 member)
- MeteorologicalYear (0 members)
- Dicke (2 members)
- Airplane (0 members)
- Mega (0 members)
- Magnetic (0 members)
- EnergyBalance (0 members)
- Circular (0 members)