Forms of energy not derived from fossil fuels include both renewable and alternative energy, terms which are sometimes used interchangeably. Alternative energy refers to any energy that isn’t fossil fuels, but does not necessarily come from a renewable source. For example, nuclear power, or energy harnessed from nuclear reactions, most commonly uses uranium, an abundant but not technically renewable fuel. Renewable energy, on the other hand, includes sources like sunlight and wind that occur naturally and continuously, though they must be harnessed and converted for use by humans. Although not completely without negative environmental impacts, renewable and alternative energy sources are often categorized as “clean energy” due to the significantly fewer carbon emissions they produce when compared to fossil fuels. Despite the environmental benefits, renewable and alternative energy sources can have their own drawbacks, though often not on the same scale as fossil fuels.