radioactive substance

n (medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance

as of stored charge or current n the organic phenomenon of rotting n an inferior state resulting from the process of decaying n the spontaneous disintegration of a radioactive substance along with the emission of ionizing radiation v lose a stored charge, magnetic flux, or current v fall into decay or ruin v undergo decay or decomposition

n the time required for something to fall to half its initial value (in particular, the time for half the atoms in a radioactive substance to disintegrate)

the chemistry of radioactive substances

a medical specialist who uses radioactive substances and X-rays in the treatment of disease