- a rare-earth, metallic element present in certain minerals and yielding colorless salts. Symbol: Tb; atomic number: 65; atomic weight: 158.924; specific gravity: 8.25.
- a soft malleable silvery-grey element of the lanthanide series of metals, occurring in gadolinite and monazite and used in lasers and for doping solid-state devices. Symbol: Tb; atomic no: 65; atomic wt: 158.92534; valency: 3 or 4; relative density: 8.230; melting pt: 1356°C; boiling pt: 3230°C
