Physics.
the time required for a collection of atoms of a particular radionuclide to decay to a fraction of the initial number equal to 1/e. Cf. e (symbol) (def. 1). Also called mean life .
DECAY TIME
Meaning of DECAY TIME in English
Random House Webster's Unabridged English dictionary. Полный английский словарь Вебстер - Random House . 2012