How is an ocarina different from other vessel flutes?

An ocarina is a type of vessel flute, which is an aerophone with a closed, typically spherical body, a blowhole, and sometimes finger holes. While many vessel flutes are made from materials like gourds, shells, or pottery, ocarinas are often made of clay or metal.1

A key distinction of the ocarina is its use of the fipple flute principle, meaning it has a duct that directs air from the blowhole to an edge. This design is similar to traditional carnival whistles. Ocarinas typically feature eight finger holes and two thumbholes, and may also include a tuning plunger. This contrasts with some other vessel flutes, which might not have these specific features or the guiding duct.21