Tb vs terbium

Tb and terbium both are nouns.

Word	Noun	Adjective	Verb	Adverb
Tb	Yes	No	No	No
terbium	Yes	No	No	No

As nouns, Tb and terbium are synonyms defined as:

Tb and terbium: a metallic element of the rare earth group; used in lasers; occurs in apatite and monazite and xenotime and ytterbite

Other synonyms of Tb include atomic number 65.

Tb (noun)	terbium (noun)
a unit of information equal to 1000 gigabits or 10^12 (1,000,000,000,000) bits	a metallic element of the rare earth group; used in lasers; occurs in apatite and monazite and xenotime and ytterbite
a metallic element of the rare earth group; used in lasers; occurs in apatite and monazite and xenotime and ytterbite