Category Nuances for null:

• metal,
• thermoelectric,
• metallic,
• absorptive,
• useful,
• insoluble,
• catalytic,
• chemical,
• covalent,
• simple,
• nonreflective,
• opaque,
• light,
• inorganic,
• coloured,
• raw,
• positive,
• real,
• powdered,
• exotic,

Simple Categories for null:

• compound,
• material,
• oxide,
• mineral,
• particle,
• affinity,