- alumAn astringent salt, usually occurring in the form of pale crystals, much used in the dyeing and tanning trade and in certain medicines, and now understood to be a double sulphate of potassium and aluminium (K₂SO₄·Al₂(SO₄)₃·24H₂O).
- aluminaAluminum oxide, especially when used in mining, material sciences or ceramics, a refractory solid compound.