Carbon forms covalent single, double, and triple bonds to a variety of atoms. Carbon can bond with itself, which leads to an almost limitless number of organic molecules. This chapter discusses the structural features and nomenclature of a class of organic molecules with only carbon and hydrogen. The linear chain of an alkane can have other attached carbon atoms. Generating carbon chains of different lengths will lead to many different compounds. The nomenclature system used is based on the number of carbon atoms in the longest continuous chain. An alkyl substituent can be attached to any of the different carbon atoms of the longest linear chain except the terminal carbons because that would simply give a longer continuous chain. Methane has an interesting relationship with biology.