impermanent; fleeting; quicly passing away
During my transitory interest in cosmology, I bought about fifty books on the subject, which ended up just sinning unread on my bookshelf.
trans (over, across)#ire (to go) (Latin)
ephemeral, evanescent, transient, transitory
enduring, immutable, perennial
Transistors take a very short time to turn from on to off i. e acting like a switch