IPA: //viˌoʊlənˈtʃɛloʊ//
KK: /viəˈlɒnˌtʃɛloʊ/
A string instrument that is larger than a violin and has a deep, rich sound, typically played while seated and held between the knees.
She played a beautiful melody on her violoncello during the concert.
Violoncello is derived from "violone" (meaning large viola) and "cello" (a diminutive form of "cello", meaning small). The term refers to a smaller version of the larger string instrument, the viola, thus indicating its size and type within the string family.
Think of a 'large viola' ('violone') that is 'small' ('cello') — this helps you remember that a violoncello is a smaller string instrument in the viola family.
No commonly confused words.