nanotube vs carbon nanotube

nanotube and carbon nanotube both are nouns.

Word	Noun	Adjective	Verb	Adverb
nanotube	Yes	No	No	No
carbon nanotube	Yes	No	No	No

As nouns, nanotube and carbon nanotube are synonyms defined as:

nanotube and carbon nanotube: a fullerene molecule having a cylindrical or toroidal shape

nanotube (noun)	carbon nanotube (noun)
a fullerene molecule having a cylindrical or toroidal shape	a fullerene molecule having a cylindrical or toroidal shape