evanescent

1. Disappearing, vanishing.Examples: "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)."Antonyms: nonevanescent

2. Disappearing, vanishing.Examples: "[…] 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?"; "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."Antonyms: nonevanescent

3. Ephemeral, fleeting, momentary.Examples: "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."; "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."Antonyms: nonevanescent, eternal, lasting, perennial, persistent