Electrical Code…
The common point on a wye-connection in a polyphase system, or midpoint on a single-phase 3-wire system, or midpoint of a single-phase portion of a 3-phase delta system, or midpoint of a 3-wire direct-current system.
Informational Note: At the neutral point of the system, the vectorial sum of the nominal voltages from all other phases within the system that utilize the neutral, with respect to the neutral point, is zero potential.
(National Electrical Code® 100-1)