【Transient】 , 【transitory】 , 【passing】 , 【ephemeral】 , 【momentary】 , 【fugitive】 , 【fleeting】 , 【evanescent】 , 【short-lived】 are comparable when they mean lasting or staying only for a short time.
【Transient】 and 【transitory】 are often used as if they were interchangeable; but 【transient】 more frequently applies to what is actually short in its duration or stay and 【transitory】 , like its close synonym 【passing】 , to what is by its nature or essence bound to change, pass, or come to an end sooner or later.
【Ephemeral】 may imply existence for only a day. In extended use, it implies marked shortness of life or of duration (as of influence or appeal).
【Momentary】 implies duration for a moment or a similar very short time.
【Fugitive】 and 【fleeting】 apply to what passes swiftly, and is gone; but 【fugitive】 carries a stronger implication of the difficulty of catching or fixing and 【fleeting】 , of the impossibility of holding back or restraining from flight.
【Evanescent】 implies momentariness, but it stresses quick and complete vanishing, and it usually connotes a delicate, fragile, or airy quality.
【Short-lived】 implies extreme brevity of life or existence often of what might be expected to last or live longer.
