Physics deals with matter and energy and the fundamental forces of nature that govern the interactions between particles. Physicists study a wide range of physical phenomena, from the sub-nuclear particles of which all ordinary matter is made (particle physics) to the material Universe as a whole (cosmology).
Some of the properties studied in physics are common to all material systems, such as the conservation of energy. Such properties are often referred to as laws of physics. Physics is sometimes said to be the "fundamental science", because each of the other natural sciences (biology, chemistry, geology, etc.) deals with particular types of material systems that obey the laws of physics. For example, chemistry is the science of molecules and the chemicals that they form in the bulk. The properties of a chemical are determined by the properties of the underlying molecules, which are accurately described by areas of physics such as quantum mechanics, thermodynamics, and electromagnetism.
Physics is closely related to mathematics. Physical theories are almost invariably expressed using mathematical relations, and the mathematics involved is generally more complicated than in the other sciences. The difference between physics and mathematics is that physics is ultimately concerned with descriptions of the material world, whereas mathematics is concerned with abstract patterns that need not have any bearing on it. However, the distinction is not always clear-cut. There is a large area of research intermediate between physics and mathematics, known as mathematical physics, devoted to developing the mathematical structure of physical theories.