Category Nuances for null:

• metal,
• dangerous,
• rare,
• invisible,
• inert,
• simple,
• out,
• safe,
• hydrophobic,
• propellant,
• noble,
• pure,
• incombustible,
• auxiliary,
• refrigerated,
• natural,
• monatomic,
• nonpolar,
• classical,
• number,
• impure,
• heavy,
• reactive,
• volatile,
• monoatomic,
• working,
• cold,
• lighter,
• popular,
• desirable,
• dry,
• useful,
• ordinary,
• electropositive,
• single,
• permanent,
• compressed,
• particular,
• unique,
• inorganic,
• valuable,
• liquid,
• conductive,
• moving,
• technical,
• chemical,
• molecular,
• foreign,
• light,
• luminous,
• harmful,
• protective,
• expensive,
• clean,
• important,
• familiar,
• dense,
• inexpensive,
• base,
• thin,
• industrial,
• available,
• controlled,
• nontoxic,
• liquified,
• ambient,
• frozen,
• neutral,
• fixed,
• hot,
• supercritical,
• atomic,
• noncombustible,
• real,
• special,
• large,
• third,
• nonflammable,
• heavier,
• liquefied,
• small,
• soluble,
• elemental,
• compressible,
• heated,
• diamagnetic,
• intermediate,
• abundant,
• rarefied,
• complex,
• atmospheric,
• individual,
• gaseous,
• cryogenic,
• dissolved,
• combustible,
• secondary,
• environmental,
• corrosive,
• medical,
• common,
• larger,
• conventional,
• nonmetallic,
• transparent,
• insoluble,
• radioactive,
• raw,
• innocuous,
• external,
• realistic,
• suitable,
• saturated,
• stable,

Simple Categories for null:

• atom,
• component,
• atmosphere,
• solid,
• gas,
• fluid,
• element,
• material,
• substance,
• constituent,
• liquid,
• matter,
• affinity,
• system,
• air,
• solute,
• part,