Oh (o), interj. [See O, interj. ] An exclamation expressing various emotions, according to the tone and manner, especially surprise, pain, sorrow, anxiety, or a wish. See the Note under O.

Ohm (om), n. [So called from the German electrician, G. S. Ohm.] (Elec.) The standard unit in the measure of electrical resistance, being the resistance of a circuit in which a potential difference of one volt produces a current of one ampere. As defined by the International Electrical Congress in 1893, and by United States Statute, it is a resistance substantially equal to 10⁹ units of resistance of the C. G. S. system of electro-magnetic units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice 14.4521 grams in mass, of a constant cross-sectional area, and of the length of 106.3 centimeters. As thus defined it is called the international ohm. Ohm’s law (Elec.), the statement of the fact that the strength or intensity of an electrical current is directly proportional to the electro-motive force, and inversely proportional to the resistance of the circuit.