Nature (also called the material world, the material universe, the natural world, and the natural universe) is all matter and energy, especially in its essential form. Nature may refer to the general realm of various types of living plants and animals, and in some cases to the processes associated with inanimate objects - the way that particular types of things exist and change of their own accord, such as the weather and geology of the Earth, and the matter and energy of which all these things are composed. It is often taken to mean the "natural environment" or wilderness - wild animals, rocks, forest, beaches, and in general those things that have not been substantially altered by human intervention, or which persist despite human intervention.