Alkanes (also known as paraffins or saturated hydrocarbons) are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds (i.e., they are saturated compounds) without any cycles (or loops; i.e., cyclic structure). Alkanes belong to a homologous series of organic compounds in which the members differ by a constant relative molecular mass of 14. They have 2 main commercial sources, crude oil and natural gas.