"Ground" as relates to electrical circuits can vary in meaning depending on the circuit. I personally agree that the "ground" of an automotive electrical system (a DC system) almost universally refers to the negative side of the battery which is "bonded" to the vehicle's frame. "Ground" in a DC circuit actually refers to 0V. Some DC electrical systems can have a positive voltage, a ground, and a negative voltage. One example are your desktop computer power supplies which can have a +12V, a ground, and a -12V. The voltages are with respect to "ground." A voltage measurement between the +12V wire and the -12V will show 24V. "Ground" in a household AC system means just that, earth ground. For safety reasons, the neutral is often bonded to ground. I hope that makes it more muddy to everyone
