Gasoline or petrol is a transparent, petroleum-derived oil that is used primarily as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain ethanol as an alternative fuel. In North America, the term gasoline is often shortened in colloquial usage to gas, despite the ambiguity created by the latter term's scientific association with non-liquids in gaseous form. This requires petroleum fuel in a gaseous state to be referred to as natural gas to avoid confusion with liquid "gas". Elsewhere petrol is the common name in the UK, Republic of Ireland, Australia and in most of the other Commonwealth countries. Under normal conditions, its physical state is a liquid, and it petroleum-derived name avoids confusion with liquefied petroleum gas or natural gas.