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[fluhk-shuh n] /ˈflʌk ʃən/
an act of flowing; a flow or flux.
Mathematics. the derivative relative to the time.
1535-45; < Middle French < Late Latin fluxiōn- (stem of fluxiō) a flowing. See flux, -ion
Related forms
fluxional, fluxionary, adjective
fluxionally, adverb Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for fluxional


(maths, obsolete) the rate of change of a function, especially the instantaneous velocity of a moving body; derivative
a less common word for flux (sense 1), flux (sense 2)
Derived Forms
fluxional, fluxionary, adjective
fluxionally, adverb
Word Origin
C16: from Late Latin fluxiō a flowing
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Article for fluxional


in mathematics, the original term for derivative (q.v.), introduced by Isaac Newton in 1665. Newton referred to a varying (flowing) quantity as a fluent and to its instantaneous rate of change as a fluxion. Newton stated that the fundamental problems of the infinitesimal calculus were: (1) given a fluent (that would now be called a function), to find its fluxion (now called a derivative); and, (2) given a fluxion (a function), to find a corresponding fluent (an indefinite integral). Thus, if y = x3, the fluxion of the quantity y equals 3x2 times the fluxion of x; in modern notation, dy/dt = 3x2(dx/dt). Newton's terminology and notations of fluxions were eventually discarded in favour of the derivatives and differentials that were developed by G.W. Leibniz. See also calculus

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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