carbon

The chemical element (symbol C) with an atomic number of 6.

A piece of carbon paper.

Example: Make sure the carbon is facing the second sheet of paper, before rolling it into the typewriter.

A carbon copy.

A fossil fuel that is made of impure carbon, such as coal or charcoal.

Carbon dioxide, when talking about global warming and climate change.

Example: A carbon footprint is a figure that measures how much carbon dioxide an activity adds to the atmosphere.