Ground or earth in a mains (AC power) electrical wiring system is a conductor that provides a low impedance path to the earth to prevent hazardous voltages from appearing on equipment (the terms "ground" (North American practice) and "earth" (most other English-speaking countries) are used synonymously here). Normally a grounding conductor does not carry current.
Neutral is a circuit conductor (that carries current in normal operation), which is connected to earth (or ground) generally at the service panel with the main disconnecting switch or breaker.
In a polyphase or three-wire (single-phase) AC system, the neutral conductor is intended to have similar voltages to each of the other circuit conductors. By this definition, a circuit must have at least three wires for one to serve as a neutral.
In the electrical trade, the conductor of a 2-wire circuit that is connected to the supply neutral point and earth ground is also referred to as the "neutral". This is formally described in the US and Canadian electrical codes as the "identified" circuit conductor.
The NEC and Canadian electrical code only define neutral as the first of these. In North American use, the second definition is used in less formal language but not in official specifications. In the UK the IET definition of a neutral conductor is one connected to the supply system neutral point, which includes both these uses.All neutral wires of the same electrical system should have the same electrical potential, because they are all connected together through the system ground. Neutral conductors are usually insulated for the same voltage as the line conductors, with interesting exceptions