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Something evanescent is there and then it is gone. It does not last. A smell of rain, a blush, morning mist over the river, a fashion that everyone loves for two weeks — those can all be evanescent. The word does not mainly mean “weak” or “”; it means the thing is real, but short. It is a literary, rather fancy adjective. In ordinary talk people say short-lived, , or it didn’t last. You will meet evanescent in novels, essays, and some science writing (there is a technical “evanescent wave,” which is a different, specialist use). Though actually, even in careful prose it can sound a little dressed-up, as if the writer is reaching for a pretty word. That is not wrong; it is just not the first word a student needs in a shop or a classroom. Use it when you want the itself to be the point.
轉瞬即逝的、稍縱即逝的（文雅字）
組成From French évanescent, from Latin ēvānēscēns, “disappearing.” Built as ē- / ex- “away, out” + vānēscō “to vanish,” from vānus “empty” plus a Latin ending that means “to become.” So: to become empty, to fade out.
同家族的字
- vanishthe everyday verb from the same Latin fading-away family
- evanescencethe noun: the quality of not lasting
- vainfrom the same Latin vanus, “empty” — though the English meanings have drifted
原始詞典資料6 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
evanescentadj/ɛvəˈnɛs(ə)nt/
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Disappearing, vanishing.
- He cannot ſuppreſs his diſapprobation […] of thoſe evaneſcent echoes of ſchool philoſophy, faint-warbling through the grove of letters, to the injury of natural and ſcientific knowledge, and the annoyance of English literature.
- The sea was each little bird's great playmate. […] In their airy flutterings, they seemed to rest on the evanescent spray.
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electrical-engineeringelectromagnetismengineeringDisappearing, vanishing.
- 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.
- 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).
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mathematicssciencesDisappearing, vanishing.
- […] I choſe rather to reduce the demonſtrations of the following propoſitions to the firſt and laſt ſums and ratio's of naſcent and evaneſcent quantities, that is, to the limits of thoſe ſums and ratio's; […] Perhaps it may be objected, that there is no ultimate proportion of evaneſcent quantities; becauſe the proportion, before the quantities have vaniſhed, is not the ultimate, and when they are vaniſhed, is none. […] [B]y the ultimate ratio of evaneſcent quantities is to be underſtood the ratio of the quantities, not before they vaniſh, nor afterwards, but with which they vaniſh.
- 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?
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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.
- 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.
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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; […]
- 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!
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biologybotanynatural-sciencesEphemeral, fleeting, momentary.
- Upward it [the "apennine adonis", probably the Pyrenean pheasant's eye (Adonis pyrenaica)] is of a pale green, with ſome Tinge of yellowiſh; and it is all the Way duſted with little grey tranſparent Globules. Theſe are the Extremities of ſo many round evaneſcent ſecretory Ducts; as the Hairs of other Plants are the more permanent Extremities of theirs.
- Per[ianth]. Berry from the receptacle elongated into a cup globular, ſucculent, gaging at the top, colour'd, at length waſting from dryneſs, evaneſcent.
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。