Carbon is an essential element in steel, it is added in specific amounts to control the hardness and strength of the material.

In general, increased carbon content reduces ductility but increases tensile strength and the ability of the steel to harden when cooled rapidly from elevated temperatures.

As an element forming a large number of compounds, many of which have important uses. Diamond and graphite are among the main forms of carbon. Coals are elemental carbon mixed with varying amounts of carbon compounds; coke and charcoal are nearly pure carbon. All organic compounds, such as proteins, carbohydrates, and fats, contain carbon, and all plant and animal cells consist of carbon compounds and their polymers.