A variant form of dynamoelectric, relating to the conversion between mechanical and electrical power.
From dynamoelectric + -al (variant adjective suffix). This form appeared alongside the -ic version but became less standard as technical terminology simplified over time.
The existence of both '-ic' and '-ical' forms of the same technical term shows how 19th-century engineers hadn't yet standardized their vocabulary—similar battles played out in electricity, chemistry, and medicine.
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