(physics) a radioactive isotopes of carbon, ¹⁴₆C, having six protons and eight neutrons; it is used in radiocarbon dating

(physics) the less common of the two stable isotopes of carbon, ¹³₆C, having six protons and seven neutrons

(chemistry) The lithium salt of carbonic acid, Li₂CO₃, used in the manufacture of glass and ceramics, and medically, in the treatment of bipolar disorder.

The physical cycle of carbon through the Earth’s biosphere, geosphere, hydrosphere and atmosphere that includes such processes as photosynthesis, decomposition, respiration and carbonification.

the overuse, by an individual or state, of the carbon dioxide absorption capacity of the world's oceans, vegetation and soil

(chemistry) the vertical group of the periodic table containing carbon, silicon, germanium, tin and lead; the elements have a valence of 4, and show the typical gradation from nonmetal to metal

any nanostructure of graphene layers arranged as stacked cones, cups or plates

A reduction in carbon dioxide emission by a third party purchased by a heavy carbon dioxide producer as part of carbon emissions trading.

a process whereby trees and other plants remove carbon dioxide from the atmosphere and through photosynthesis, turn it into plant material

(physics) The most abundant of the two stable isotopes of carbon, ¹²₆C, having six protons and six neutrons; it is the standard for atomic weight and is used to define the mole.