Half+Life

Half-life
Clarify the meaning of ‘half-life’.

Half-life is the period of time it takes for a substance undergoing decay to decrease by half. The name originally was used to describe a characteristic of unstable atoms (radioactive decay), but may apply to any quantity which follows a set-rate decay. Each particular particle has its own halflife.The original term, dating to 1907, was "half-life period", which was later shortened to "half-life" in the early 1950s.