evanescent

Etymology

Borrowed from French évanescent (“evanescent”), from Latin ēvānēscēns (“disappearing, vanishing”), present participle of ēvānēscō (“to disappear, vanish; to die out, fade away; to lapse”), from ē- (variant of ex- (prefix meaning ‘away, out’)) + vānēscō (“to vanish”) (from vānus (“empty, vacant, void”), from Proto-Indo-European *h₁weh₂- (“to abandon, leave”)) + -ēscō (suffix forming verbs with the sense ‘to become’)).

adj

1. Disappearing, vanishing.
   1. (electromagnetism) Of an oscillating electric or magnetic field: not propagating as an electromagnetic wave but having its energy spatially concentrated in the vicinity of its source.
      Consequently, the electromagnetic fields have plane-wave characteristics in local regions, except immediately adjacent to a caustic where there is a rapid transition from the wavelike behavior of the local plane-wave fields to the evanescent behavior beyond the ray path. 1983, Allan W[hitenack] Snyder, John D[avid] Love, “Rays and Local Plane Waves”, in Optical Waveguide Theory (Science Paperbacks; 190), London, New York, N.Y.: Chapman & Hall; republished Boston, Mass., Dordrecht: Kluwer Academic Publishers, 2000, section 35—4 (Component Equations of the Ray-path Equation), page 671
      The analyte directly affects the optical properties of a waveguide, such as evanescent waves (electromagnetic waves generated in the medium outside the optical waveguide when light is reflected from within) or surface plasmons (resonances induced by an evanescent wave in a thin film deposited on a waveguide surface). 2015, Yitzhak Mendelson, “Optical Sensors”, in Joseph D. Bronzino, Donald R. Peterson, editors, Medical Devices and Human Engineering (Biomedical Engineering Handbook; 2), 4th edition, Boca Raton, Fla.: CRC Press, section I (Biomedical Sensors), page 6-1
   2. (mathematics) Of a number or value: diminishing to the point of reaching zero as a limit; infinitesimal.
      And what are theſe Fluxions? The Velocities of evaneſcent Increments? And what are theſe ſame evaneſcent Increments? They are neither finite Quantities, nor Quantities infinitely ſmall, nor yet nothing. May we not call them the Ghoſts of departed Quantities? 1734, [George Berkeley], The Analyst; or, A Discourse Addressed to an Infidel Mathematician.[…], London: Printed for J[acob] Tonson[…], →OCLC, section XXXV, page 59
      Some hold the evaneſcent increments to be real quantities, ſome to be nothings, ſome to be limits. As many Men, ſo many minds: Each differing one from another, and all from Sir Iſaac Newton. 1735, [George Berkeley], A Defence of Free-thinking in Mathematics.[…], London: Printed for J[acob] Tonson, →OCLC, paragraph XLIV, page 55
      [Leonhard] Euler emphasized that the derivative is the ratio of the evanescent differentials and said that the integral calculus was concerned with finding the function itself. 1972, Morris Kline, “Calculus in the Eighteenth Century”, in Mathematical Thought from Ancient to Modern Times, New York, N.Y.: Oxford University Press; paperback edition, volume 2, New York, N.Y., Oxford, Oxfordshire: Oxford University Press, 1990, section 3 (The Technique of Integration and Complex Quantities), page 406
2. Barely there; almost imperceptible.
   If the Fluids moving in an Evaneſcent Artery [i.e., a capillary] appear Globular, I ſuppose its becauſe the Canal is round, which alters the Caſe much. 22 August 1709, Archibald Adams, “IV. A Letter from Dr. Archibald Adams to Dr. Hans Sloane, R[oyal] S[ociety] Secr[etary], Concerning the Manner of Making Microscopes, &c. Norwich, August 11, 1709 [Julian calendar]”, in Philosophical Transactions. Giving Some Account of the Present Undertakings, Studies, and Labours of the Ingenious, in Many Considerable Parts of the World, volume XXVII, number 325, London: Printed for H. Clements[…], and W. Innys[…], and D. Brown[…], published January–March 1710 (1712 printing), →OCLC, page 26
   Here are Sholes and Sholes, of various Characters, and of the moſt diverſified Sizes; from the gigantic Whale, whoſe flouncings "tempeſt the Ocean," to the evaneſcent Anchovy, whoſe Subſtance diſſolves in the ſmalleſt Fircaſſee. 1767, James Hervey, “Letter IX. Theron to Aspasio.”, in Theron and Aspasio: Or, A Series of Dialogues and Letters, upon the Most Important and Interesting Subjects. In Three Volumes, 5th edition, volume III, London: Printed by Charles Rivington, for John and Francis Rivington,[…], →OCLC, page 163
   If in the middle of summer the water of Turkey Creek […] is whipped and beaten with a stick, and then if a fire-brand is passed over, a mist is enkindled and a faint evanescent flame runs over the entire width of the brook. 1911, Johann David Schoepf [i.e., Johann David Schoepff], “Return from Pittsburgh”, in Alfred J. Morrison, transl., Travels in the Confederation [1783–1784]: From the German, volume I (New Jersey, Pennsylvania, Maryland, Virginia), Philadelphia, Pa.: William J. Campbell, →OCLC, page 290
   If we could remove everything from a piece of space, […] then there would still be quantum fluctuations of fields and virtual particles, bouncing to and fro against the wall of nothing. Ironically enough, this piece of space, filled with so many evanescent entities, is nowadays called vacuum. However, this vacuum is not nothing. It is a quantum vacuum to which the argument of the Ancient Greeks does not apply. 2013, Gérard Gousbet, “Understanding Quantum Mechanics”, in Hidden Worlds in Quantum Physics, Mineola, N.Y.: Dover Publications, page 394
3. Ephemeral, fleeting, momentary.
   It is to be obſerved, farther, that when we annihilate any thing in our Mind, we conſider it as ſomething evaneſcent, and removed out of Sight; […] 1732, William King, “Containing Some Principles Previously Necessary to the Understanding and Solution of the Difficulty about the Origin of Evil”, in Edmund Law, transl., An Essay on the Origin of Evil. […] Translated from the Latin,[…], 2nd corrected and enlarged edition, London: Printed by J. Stephens, for W. Thurlbourn[…]; and sold by J. Knapton, R. Knaplock and W. Innys[…], →OCLC, section II (Of the Enquiry after the First Cause), paragraph X, page 33
   But alas! how momentary was the bliss!—the evaneſcent viſion ſoon fled, and the youthful queen Mary, Queen of Scots] was arrayed in the melancholy garb of widowhood! 1798 February, “Constantia” [pseudonym; Judith Sargent Murray], “No. XLVII”, in The Gleaner. A Miscellaneous Production. In Three Volumes, volume II, printed at Boston, Mass.: By I. Thomas and E. T. Andrews,[…], →OCLC, page 138
   1. (botany) Of plant parts: shed after a period.
      Leaves solitary or numerous, sometimes evanescent or rarely wanting, radical or cauline, alternate or occasionally whorled, simple, varying from a sheathing bract to a definite blade which is membranaceous, papyraceous, coriaceous or fleshy, flat or plicate, usually parallel-veined. 1960, Richard Evans Schultes, “Orchidaceae A. L. de Jussieu”, in Native Orchids of Trinidad and Tobago (International Series of Monographs on Pure and Applied Biology: Botany Division; 3), Oxford, Oxfordshire, New York, N.Y.: Pergamon Press, →OCLC, page 19