Sunfast

Part of speech: adjective

Definitions

1. A quality found in specific textiles indicating that their colors endure prolonged exposure to sunlight without losing vibrancy
2. A term describing a property in certain materials that allows them to retain their color brilliance despite extended exposure to solar radiation
3. Having the ability to maintain original colors despite prolonged exposure to sunlight

Etymology: "Sunfast" is a plain compound: "sun," from Old English "sunne," joined to "fast," from Old English "fæst," meaning firm or fixed. Put together, the word describes fabric whose dye is fixed firmly enough to withstand sunlight. The sense of "fast" here is the older one, in which a colour is "fast" when it does not run or fade, the same sense found in "colourfast." Textile makers used that idea for centuries before "sunfast" became a standard label for fabrics tested against prolonged light exposure, and the compound simply names the specific threat, the sun, that the dye must survive.

Synonyms: lightfast