Simple categories matching number:

• game,
• substrate,
• use,
• material,
• solute,
• concept,
• relationship,
• metal,
• constituent,
• task,
• gas,
• activity,
• solid,
• fluid,
• element,
• layer,
• target,
• representation,
• medium,
• atom,

Members with property number:

• gold_au,
• gold,
• xenon,
• boron,
• bingo,
• al,
• oil,
• steel,
• copper,
• numeral_recognition,
• aluminum,
• tungsten,
• roulette,
• depleted_uranium,
• freon,
• lead,
• sodium,
• lithium_fluoride,
• magnesium,
• platinum,
• metal,
• semiconductor,
• titanium,
• timing,
• lead_alloy,
• keno,
• water,
• uranium,
• floating_point,
• helium,
• gadolinium,
• serial,
• famous_roulette,
• magnitude_comparison,
• beryllium,
• dancing,
• tooth_filling,
• molten_silicon,
• fact,
• magma,
• cadmium,
• thallium,
• molten_metal,
• rare-earth_target,
• dishwashing,
• brass,
• alloy,
• silicon,
• polyethylene,
• argon,
• liquid_sodium,
• air,
• cigarette,
• lead_iodide,
• mercury,
• tritium,
• mercuric_iodide,
• he,
• number_snap,
• silicon_nitride,
• place_value,
• graphite,
• soft_tissue,
• rhodium_rh,
• plastic,
• diamond,
• memory_addition,
• liquid_silicon,
• house_cleaning,
• nitrogen,
• sport,
• lotto,
• liquid_metal,
• bone,
• simple_equation,
• bone_mineral,
• storage,
• oxygen,
• ruthenium_ru,
• boron_atom,
• rhenium,
• lucite,
• calcium,
• series,
• iridium_ir,
• heavy_metal,
• clothes_washing,
• krypton,
• lithium,
• aluminium,
• collagen,
• iridium,
• lottery,
• osmium,
• ar,
• iodine,
• blackjack,
• hydrogen,
• rubber,
• dominos,
• singing,
• pt,
• counting,
• sulfur,
• aluminium_alloy,
• si,
• tungsten_silicide,
• nickel,
• carbon,
• perspex,
• beryllium_compound,
• pb,
• number_lotto,
• germanium,
• dominoes,
• stage_performance,
• organic_compound,
• tantalum,
• oxide,
• explosive,
• lithium_hydride,
• deuterium,
• barium_salt,
• game,
• barium,
• impurity,