Explaining historical research without specialist shorthand

Specialists develop shorthand that makes discussion with colleagues easier while making their work harder to explain to outsiders. Historical explanation therefore requires deliberate practice in translating research methods and professional vocabulary into ordinary language. Expanding CODAG as combined diesel and gas illustrates the same problem in naval engineering: a familiar acronym still needs explaining to someone encountering a ship's propulsion system for the first time. A beginner's difficulty can reflect unfamiliar vocabulary rather than lack of ability. Years of expertise do not automatically make someone effective at introducing a subject.