radioactive
Meaning of radioactive: Radioactive describes a substance whose unstable atomic nuclei give off energy as radiation while decaying into more stable forms.
Definition of radioactive
Radioactive describes a material whose atomic nuclei are unstable and release energy in the form of radiation as they change into a more stable configuration. This process, called radioactive decay, occurs at a predictable rate for a given substance and can release particles, electromagnetic energy, or both.
Radioactive materials are used clinically in controlled and measured ways for both diagnosis and treatment. Diagnostic imaging techniques such as certain nuclear medicine scans use a small amount of a radioactive tracer to visualize organ function, while some cancer treatments use radioactive sources placed near or within a tumor to deliver radiation directly to it.
Radioactive materials are handled under specific safety protocols because radiation exposure carries risks that depend on the type, amount, and duration of exposure.
Used in a sentence
A radioactive tracer was injected before the nuclear medicine scan.
Good to know
Radioactive and irradiated describe different things: a radioactive substance itself emits radiation, while an irradiated object has been exposed to radiation from an outside source and does not necessarily become radioactive itself.
Word origin
Where “radioactive” comes from
Formed from radio- (from Latin radius, meaning "ray") and active, from Latin activus, meaning "acting."