Atomic_number_5WordNet Explorer

a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder

any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter

a light soft mineral consisting of hydrated sodium borate in crystalline form; an important source of boron

an ore of boron consisting of hydrated sodium borate; used as a flux or cleansing agent