White is a color, the perception of which is evoked by light that stimulates all three types of color sensitive cone cells in the human eye in nearly equal amounts and with high brightness compared to the surroundings. A white visual stimulation will be void of hue and grayness.

White light can be generated in many ways. The sun is such a source, electric incandescence is another. Modern light sources are fluorescent lamps and light-emitting diodes. An object whose surface reflects back most of the light it receives and does not alter its color will appear white, unless it has very high specular reflection.

Since white is the extreme end of the visual spectrum (in terms of both hue and shade), and since white objects - such as clouds, snow and flowers - appear often in nature, it has frequent symbolism. Human culture has many references to white, often related to purity and cleanness, whilst the high contrast between white and black is often used to represent opposite extremes.

The word white continues Old English hwīt, ultimately from a Common Germanic *χ^wītaz also reflected in OHG (h)wîz, ON hvítr, Goth. ƕeits. The root is ultimately from Proto-Indo-European language *k^wid-, surviving also in Sanskrit śveta "to be white or bright" and Slavonic světŭ "light". The Icelandic word for white, hvítur, is directly derived from the Old Norse form of the word hvítr. Common Germanic also had the word *blankaz ("white, bright, blinding"), borrowed into Late Latin as *blancus, which provided the source for Romance words for "white" (French blanc, Spanish blanco, Italian bianco, etc.). The root survives in English in the word black.

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica (silicon dioxide, or SiO₂), usually in the form of quartz.

The second most common form of sand is calcium carbonate, for example aragonite, which has mostly been created, over the past half billion years, by various forms of life like coral and shellfish. It is, for example, the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years, like the Caribbean.

In terms of particle size as used by geologists, sand particles range in diameter from 0.0625 mm (or ⅟16 mm) to 2 mm. An individual particle in this range size is termed a sand grain. Sand grains are between gravel (with particles ranging from 2 mm up to 64 mm) and silt (particles smaller than 0.0625 mm down to 0.004 mm). The size specification between sand and gravel has remained constant for more than a century, but particle diameters as small as 0.02 mm were considered sand under the Albert Atterberg standard in use during the early 20th century. A 1953 engineering standard published by the American Association of State Highway and Transportation Officials set the minimum sand size at 0.074 mm. A 1938 specification of the United States Department of Agriculture was 0.05 mm. Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like flour).