violoncello vs cello

violoncello and cello both are nouns.

Word	Noun	Adjective	Verb	Adverb
violoncello	Yes	No	No	No
cello	Yes	No	No	No

As nouns, violoncello and cello are synonyms defined as:

violoncello and cello: a large stringed instrument; seated player holds it upright while playing

violoncello (noun)	cello (noun)
a large stringed instrument; seated player holds it upright while playing	a large stringed instrument; seated player holds it upright while playing