In the context of physics and optics, the appearance of "white" is often defined by the reflection of a full spectrum of visible electromagnetic radiation. A material or surface that appears white is generally highly diffuse and exhibits a high degree of reflectance, meaning it scatters incoming light across the visible spectrum with minimal absorption. This property is distinct from the mere combination of colors, as true whiteness relates to the spectral uniformity of reflected light. Chemically, the term can also refer to compounds that precipitate or exist in a solid, crystalline state that lacks inherent pigmentation, such as certain metal oxides or salts. Understanding whiteness requires considering the interaction between incident light and matter, where the perceived color is determined by the wavelengths of light that are reflected back to an observer.