Radioactivity (noun)

The property exhibited by some elements of emitting energy as electromagnetic waves or as moving subatomic particles, especially alpha or beta particles, during radioactive decay.

Origin:

Late 19th century: from radio- + activity.

Examples:

1. The radioactivity was so high that it was dangerous to stay in the area.
2. The scientists were studying the radioactivity of the new mineral sample.
3. The discovery of radioactivity led to the development of nuclear power.
4. The radioactivity of the element is used to date rocks and fossils.
5. The radioactivity of the material was measured in becquerels.