carbon

1. (uncountable) The chemical element (symbol C) with an atomic number of 6. It can be found in pure form for example as graphite, a black, shiny and very soft material, or diamond, a colourless, transparent, crystalline solid and the hardest known material.Examples: "All life as we know it has carbon as the backbone of many of its molecules; carbon’s tetravalence gives it special importance in biochemical molecular bonds."; "Carbon is the most common element in our bodies—indeed, in all living things on earth."; "Fans will pump air through the alkaline stream, which causes carbon dioxide to form solid calcium carbonate, the material from which seashells are formed, which will look like a fine sand, as well as dissolved bicarbonate."uncountable

2. (countable) An atom of this element, in reference to a molecule containing it.Examples: "A methane molecule is made up of a single carbon with four hydrogens."countable

3. (countable, informal) A sheet of carbon paper.Examples: "He stepped back and opened his bag and took out a printed pad of D.O.A. forms and began to write over a carbon."countableinformal

4. (countable, informal) A carbon copy.Examples: "Please provide me with a carbon of your form."; "Press firmly: you are making a carbon."countableinformal

5. (ecology, climate change, uncountable) Ellipsis of carbon dioxide.Examples: "carbon neutral"; "carbon capture"; "If Alberta’s reserves are a carbon bomb, this global expansion of tar sands and oil shale exploitation amounts to an escalating emissions arms race, the unlocking of a subterranean cache of weapons of mass ecological destruction."abbreviationalt-ofellipsisuncountable

6. (informal) Ellipsis of carbon fiber (reinforced polymer).Examples: "carbon bike frame"abbreviationalt-ofcountableellipsisinformaluncountable