It appears that some manufacturers use the terms interchangeably. Here's from an S-70 manual, a few years old ...
One accessory module is mounted on the forward section of each input module. Each accessory module provides mounting and drive for an ac electrical generator and a hydraulic pump module.
Later in the manual, it goes on to explain that this generator supplies three phase AC power, some of which powers AC systems, and some of which goes through an inverter to provide DC power via the DC power busses.