The unit of electric resistance in the centimeter-gram-second electromagnetic system of units. A conductor has a resistance of 1 abohm when the potential difference between the two ends of the conductor is 1 abvolt when a current of 1 abampere flows through it. Symbol, abΩ. One abohm = 10⁻⁹ ohm.

The prefix ab- comes from “absolute.” See ab- for the history of this prefix, which was always more popular in the United States than elsewhere. The rise of the metric system and subsequently SI eliminated any need for this unit. By the end of the 20ᵗʰ century, it was almost out of use.

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According to the current national standard in the United States¹, the abohm is not to be used. The ohm should be used instead.

1. IEEE/ASTM SI 10™-2002.
American National Standard for Use of the International System of Units (SI): The Modern Metric System.
New York: IEEE, 30 December 2002.

See Section 3.3.3.


For an excellent history of the development of the electric and magnetic units up to 1913, see U. S. Bureau of Standards Circular 60.


Dr. Kennelly has put forward an ugly system of nomenclature for absolute electromagnetic and electrostatic units which will hardly find favour in this country. [Britain] He proposes to employ the prefixes “ab” and “abstat” to designate absolute electromagnetic and electrostatic units respectively, so that abvolt represents the electromagnetic unit of potential and abstatvolt the electrostatic unit. For euphony he suggests absohm, rather than abohm for the electromagnetic unit of resistance.

All these propositions, strange to say, have been accepted by the American Institute of Electrical Engineers. Representative institutions in all other countries have been asked to consider them, and doubtless the subject will soon be opened for discussion at the Institution of Electrical Engineers.

The Electrician, vol 52, no. 1334, page 275 (Dec. 11, 1903).

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