Efficiency, from the Oxford English Dictionary On Line

1. a. The fact of being an operative agent or efficient cause. Now only in philosophical use.

1593 HOOKER Eccl. Pol. I. i, The manner of this deuine effeciencie being farre above us. 1628 T. SPENCER Logick 31 God is sayd to be the Efficient Cause of man: the office of this efficiency, is placed in ioyning the forme vnto the matter. 1676 HALE Contempl. I. 365 The Efficiency..of the Principal Cause is that which gives efficacy to the Means and makes it effectual. 1695 WOODWARD Nat. Hist. Earth I. (1723) 56 [Gravity of bodies] does not proceed from the Efficiency of any such Contingent and unstable Agents. 1870 BOWEN Logic xii. 417 Constancy of sequence is no certain indication of causal efficiency.

b. The action of an operative agent or efficient cause; production, causation, creation. Obs.

1663 J. SPENCER Prodigies (1665) 221 These Prodigies are of Diabolical efficiency. 1677 HALE Prim. Orig. Man. IV. vii. 350 That Power and Wisdom..were equal to the formation and efficiency of the Sun. 1678 CUDWORTH Intel. Syst. 576 These ancient pagans..used it [creare] generally for all manner of production or efficiency.

2. a. Fitness or power to accomplish, or success in accomplishing, the purpose intended; adequate power, effectiveness, efficacy.

1633 AMES Agst. Cerem. I. 49 The very frame of it..had an efficiency..to cary up the heart to God. 1818-60 WHATELY Com.-pl. Bk. (1864) 76 The penalty annexed to any law is an instance, not of its efficiency, but..of its failure. 1858 BUCKLE Civiliz. (1873) II. viii. 556 The navy was..more than doubled in efficiency. 1859 MILL Liberty v. (1865) 67/2 The greatest dissemination of power consistent with efficiency. 1863 FAWCETT Pol. Econ. II. v. 193 That nothing more powerfully promotes the efficiency of labour than an abundance of fertile land.

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c. spec. in Economics, as economic, marginal, technical efficiency (see quots.).

1906 A. SHADWELL (title) Industrial efficiency. A comparative study of industrial life in England, Germany and America. 1916 A. MARSHALL Princ. Econ. (ed. 7) IV. v. 193 Health and strength, physical, mental and moral..are the basis of industrial efficiency, on which the production of material wealth depends. 1926 Industrial Management Jan. 4/1 The choice is restricted to a definitely established range of sizes and types, outside of which the designer of the average car would venture with considerable trepidation, and at the sacrifice of manufacturing efficiency. Ibid. 34 (Advt.), Sure and efficient power drives make for higher overall plant efficiency. 1936 J. M. KEYNES Gen. Theory Employment, Interest & Money IV. ii. 135 The relation between the prospective yield of a capital-asset and its supply price or replacement cost, i.e. the relation between the prospective yield of one more unit of that type of capital and the cost of producing that unit, furnishes us with the marginal efficiency of capital of that type. 1953 G. HUTTON We too can Prosper i. 13 Productivity is the efficiency..of production. 1965 J. L. HANSON Dict. Econ. & Commerce 133/1 Economic efficiency, the maximum average output per employee. Ibid., Economic efficiency is a much wider term than technical efficiency, which applies only to the efficiency of one factor of production, namely capital. 1965 SELDON & PENNANCE Everyman's Dict. Econ. 137 Economic efficiency, relates to output per unit cost of the resources employed; contrasted with technical efficiency, which measures output of energy per unit of energy applied. 1966 A. GILPIN Dict. Econ. Terms 57 Economic efficiency, the efficiency with which scarce resources are used and organised to achieve stipulated economic ends. In competitive conditions, the lower the cost per unit of output, without sacrifice of quality, in relation to the value or price of the finished article, the greater the economic efficiency of the productive organisation.

3. Mech. and Physics. a. The work done by a force in operating a machine or engine; the total energy expended by a machine. Obs.

1827 D. GILBERT in Phil. Trans. R. Soc. CXVII. 27 Since therefore a machine is efficient in producing duty, or effect, in proportion to the force applied, multiplied into the space through which it acts, I propose to denominate this function (f × s) efficiency; retaining the word duty for a similar function indicative of the work performed... By a comparison of these two quantities, the efficiency expended on any machine, and the duty performed by it, an exact measure will be ascertained of its intrinsic worth. Ibid. 31 The received efficiency of a water wheel being represented by the pounds of water passing over it × by the fall in feet, less the height due to the velocity with which the periphery moves in its rotation. 1832 W. WHEWELL First Princ. Mech. iv. 54 It has been proposed by Mr Davies Gilbert..to call the product f × s the Efficiency of the force f. Ibid. 55 The work done by any machine is always equal to the Efficiency of the moving force... But machinery may very much increase the convenience of application of the force. Ibid. 64 To find the theoretical Efficiency of a Steam Engine working for one minute.

b. The ratio of useful work performed to the total energy expended or heat taken in.
radiant or luminous efficiency, the ratio of the total luminous flux produced to the total power consumed.

1855 W. J. M. RANKINE in Proc. Philos. Soc. Glasgow III. VI. 398 Efficiency of engines. An engine is a contrivance for transforming energy by means of the periodical repetition of a cycle of variations of the accidents of a substance. The efficiency of an engine is the proportion which the energy permanently transformed to a useful form by it bears to the whole energy communicated to the working substance. 1858 Man. Appl. Mech. VI. 610 The object of improvements in machines is to bring their efficiency as near to unity as possible. 1879 G. B. PRESCOTT Speaking Telephone xiv. 465 The true comparative measure of the efficiency of dynamo-electric machines. 1887 Encycl. Brit. XXII. 496/1 The efficiency of furnace and boiler is the ratio which the amount of heat taken up by the water bears to the whole potential energy of the fuel. In good boilers this efficiency is about 0·7. 1902 Ibid. XXXIII. 418/1 The ratio between the power given out by a transformer and the power taken up by it is called its efficiency. 1929 Ibid. VIII. 290/1 The ‘efficiency’ of a lamp is measured in lumens per watt. 1958 Van Nostrand's Sci. Encycl. (ed. 3) 561/1 Usually there is a load for which the efficiency is a maximum. 1960 R. W. MARKS Dymaxion World of B. Fuller 51/1 In engineering, the term ‘efficiency’ means the ratio of foot-pounds of work realized to the foot-pounds of energy consumed by a given mechanical system. 1967 CONDON & ODISHAW Handbk. Physics (ed. 2) v. 6/1 Of all engines working between two heat reservoirs of temperature 1 and 2 (2 > 1), the reversible engine is the one of maximum efficiency.