(Redirected from Definition:Half-Life)

## Definition

The half-life of a radioactive isotope is the time it takes for exactly half of an arbitrary quantity of that isotope to undergo radioactive decay.

Thus it is the time it takes for exactly half of an arbitrary quantity of that isotope to remain.

### Examples

 Rubidium-$87$ $48.8 \times 10^9$ years Uranium-$238$ $4.5 \times 10^9$ years Potassium-$40$ $1.251 \times 10^9$ years Carbon-$14$ $5\,730 \pm 40$ years