Definition of carbon-12 in US English:

carbon-12

noun

  • The most common natural carbon isotope, of mass 12. It is the basis for the accepted scale of atomic mass units.

    • ‘In 1961 the isotope carbon-12 was selected to replace oxygen as the standard relative to which the atomic weights of all the other elements are measured.’
    • ‘The variability of the carbon-13/carbon-12 ratio in honeys was evaluated preliminary to use of the ratio to detect the addition of high-fructose corn syrup.’
    • ‘All life needs Carbon 12 to live, all plants and animals.’

Pronunciation

carbon-12

/ˌkärbənˈtwelv/