THESAURUS
ephemeral
brief, brittle, capricious, changeable, corruptible, deciduous, dying, episodic, evanescent, evergreen, fading, fickle, fleeting, flitting, fly-by-night, flying, fragile, frail, fugacious, fugitive, half-hardy, hardy, impermanent, impetuous, impulsive, inconstant, insubstantial, momentary, mortal, mutable, nondurable, nonpermanent, passing, perennial, perishable, short, short-lived, subject to death, temporal, temporary, transient, transitive, transitory, undurable, unenduring, unstable, volatile
ROGET THESAURUS
ephemeral
Transientness
N
transience, transientness, evanescence, impermanence, fugacity, caducity, mortality, span, nine days' wonder, bubble, Mayfly, spurt, flash in the pan, temporary arrangement, interregnum, velocity, suddenness, changeableness, transient, transient boarder, transient guest, transient, transitory, transitive, passing, evanescent, fleeting, cursory, short-lived,
ephemeral, flying, fugacious, fugitive, shifting, slippery, spasmodic, instantaneous, momentaneous, temporal, temporary, provisional, provisory, deciduous, perishable, mortal, precarious, unstable, insecure, impermanent, brief, quick, brisk, extemporaneous, summary, pressed for time, sudden, momentary, temporarily, pro tempore, for the moment, for a time, awhile, en passant, in transitu, in a short time, soon, briefly, at short notice, on the point of, on the eve of, in articulo, between cup and lip, one's days are numbered, the time is up, here today and gone tomorrow, non semper erit aestas, eheu! fugaces labuntur anni, sic transit gloria mundi, a schoolboy's tale, the wonder of the hour!, dum loquimur fugerit invidia aetas, fugit hora, all that is transitory is but an illusion.