When a substance is made incorporating a radioactive isotope of one of its constituent atoms, in order to help trace the movement and chemical reactions of the substance, it is said to carry a (radioactive) label. Found on http://www.encyclo.co.uk/visitor-contributions.php
When a substance is made incorporating a radioactive isotope of one of its constituent atoms, in order to help trace the movement and chemical reactions of the substance, it is said to carry a (radioactive) label.