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equilibrium|iːkwɪˈlɪbrɪəm|
Also 7–9 æquilibrium.
[a. L. æquilībrium, f. æquus equal + lībra balance.]
1. a. In physical sense: The condition of equal balance between opposing forces; that state of a material system in which the forces acting upon the system, or those of them which are taken into consideration, are so arranged that their resultant at every point is zero.
A body is said to be in stable equilibrium, when it returns to its original position after being disturbed; in unstable when it continues to move in the direction given to it by the disturbing force; in neutral, when it remains stationary in its new position.
1660Boyle New Exp. Phys. Mech. i. 36 The pressure on all hands being reduced as it were to an æquilibrium. 1697Phil. Trans. XIX. 446 The Fluids, pressing equally and easily yielding to each other, soon restore the æquilibrium. 1796Atwood Floatation ibid. LXXXVI. 51, 1st. The equilibrium of stability..2dly. The equilibrium of instability..3dly. The equilibrium of indifference. 1830Herschel Stud. Nat. Phil. 222 Thereby to maintain equilibrium. 1838J. Grant Sk. Lond. 299 Trying how fast they could run down [the hill] without losing their equilibrium. 1860Mill Repr. Govt. (1865) 6/1 A government so situated is in the condition called in mechanics unstable equilibrium, like a thing balanced on its smaller end. 1879tr. De Quatrefages' Hum. Species 4 In the crystal once formed, the forces remain in a state of stable equilibrium.
b. equilibrium of temperature: see quot.
1794J. Hutton Philos. Light, etc. 91 The supposed state of a perfect equilibrium, or equal temperature among bodies. 1871B. Stewart Heat §12 Two bodies may be said to be in a state of equilibrium of temperature with each other when if shaken together they neither change their state with respect to heat, nor, etc.
2. a. The state of equal balance between powers of any kind; equality of importance or effect among the various parts of any complex unity.
1677Govt. Venice 80 So to balance their [the Spaniard and the French] Power, as to keep both in an Equilibrium. 1741Middleton Cicero (1742) I. Pref. 38 [The two Gracchi] had in great measure overturned that æquilibrium of power in the Republic, in which its peace and prosperity depended. 1773Observ. State Poor 80 A destruction of the equilibrium of population, by a defection of inhabitants from one county to another. 1840Macaulay Ranke Ess. 1851 II. 144 The war which followed was a war for the equilibrium of Europe. 1871R. F. Weymouth Euph. 4 Of such equilibrium and symmetry in antithesis every page of the Euphues furnishes examples.
b. The condition of suspense or uncertainty produced by equality in the force of opposing influences; neutrality of judgement or volition.
1685Sharp Doubting Conscience 4 There is an end of the Doubt or æquilibrium. 1754Edwards Freed. Will i. i. 4 Where there is absolutely no preferring or chusing, but a perfect continuing Equilibrium there is no Volition. 1794Paley Evid. iii. viii. (1817) 372 That indifferency and suspense, that waiting and equilibrium of the judgement. 1876E. White Life in Christ i. vii. 74 This is the infidelity of persons..who pass their lives in a state of equilibrium or indifference.
c. Well-balanced condition of mind or feeling.
1608J. King Serm. St. Mary's 26 Salomon a man in the perfit æquilibrium and stablest state of his age. 1874Farrar Christ II. 45 In this outward activity, she lost the necessary equilibrium of an inward calm. 1875Hamerton Intell. Life x. ix. 384 It is best to preserve our minds in a state of equilibrium.
3. The Lat. in æquilibrio ‘in equilibrium’ appears usually with anglicized spelling (equi-). (The Latin ablative in this phrase was formerly sometimes treated as an Eng. word; hence such expressions as in perfect equilibrio.)
1650Bulwer Anthropomet. 229 When the body is erect and in equilibrio. 1683Pettus Fleta Min. i. (1686) 150 Weigh it..until the Ballance standeth even in æquilibrio. 1709Prior Poems, Ladle 45 Is it in equilibrio, If deities descend or no? Then let the affirmative prevail, As requisite to form my tale. 1755Gentl. Mag. XXV. 164 Being at the vernal equinox in an equilibrio. 1798T. Jefferson Writ. (1859) IV. 231 The fate of Sprigg's resolutions seems in perfect equilibrio. 1868Rogers Pol. Econ. xv. (ed. 3) 209 These bills..may exactly balance between country and country. In such a case, the trade between the two countries is said to be in equilibrio.
4. attrib. equilibrium diagram, a diagram representing the limits of temperature and composition within which the various phases or constituents of an alloy system are stable; a constitutional diagram; equilibrium moisture content (see quot. 1966).
1874Knight Dict. Mech., Equilibrium-valve..having a pressure nearly equal on both sides. 1880Haughton Phys. Geog. iii. 92 The point of equilibrium temperature, which is the Fahrenheit zero. 1925Jrnl. Iron & Steel Inst. CXII. 345 In the equilibrium diagram of the iron-carbon system..the A2 line is shown by a dotted line. 1934Webster, Equilibrium moisture content. 1948New Biol. IV. 91 Wood being a hygroscopic material adjusts itself to the moisture condition of its surroundings by losing or absorbing moisture until an equilibrium moisture content is attained. 1966A. W. Lewis Gloss. Woodworking Terms 27 Equilibrium moisture content, normal stable state of timber when its moisture content corresponds with the humidity of the air.
Add:[2.] d. spec. in Econ. A situation in which supply and demand are matched and prices stable.
1871W. S. Jevons Theory of Pol. Econ. iv. 109 In practice, no market ever long fulfils the theoretical conditions of equilibrium, because, from the various accidents of life and business, there are sure to be many people every day compelled to sell or having sudden strong inducements to buy. 1911Encycl. Brit. XVII. 731/2 Supposing equilibrium to have been attained in a given market,..the price of the commodity dealt in, in the market, will remain practically unchanged during that period. 1936J. M. Keynes Gen. Theory Employment i. iii. 26 Effective demand, instead of having a unique equilibrium value, is an infinite range of values. 1953J. L. Hanson Textbk. Econ. x. 166 Both supply and demand vary with price, and so at the equilibrium price these two forces can be balanced. 1976Economist 16 Oct. 21/3 So there is obviously a connection between balance of payments equilibrium and money market equilibrium, although the two are not the same. 1984F. Hahn (title) Equilibrium and macroeconomics. |