Is "sheen" a word?

Yes, sheen is absolutely a valid English word with a long history and multiple uses. As a common noun, sheen means a soft, smooth, luminous shine, luster, or glow on a surface, a gentle radiance caused by light reflecting evenly off a smooth material. For example, you can talk about the sheen of healthy hair, the pearly sheen of silk, or the sheen of polished wood. In paint and coatings, sheen is a technical term for gloss level. As a verb, to sheen means to shine or to cause to shine, though this usage is less common. Sheen is also a well-established surname of Irish origin, an anglicized form of O'Shea, famously borne by actors Martin Sheen and Charlie Sheen, which is also a valid use of the word as a proper noun. Additionally, Sheen or Shein is the name of a major international fast-fashion retailer. The word appears in standard English dictionaries, including Merriam-Webster and Oxford English Dictionary, and is considered common vocabulary. It is pronounced with a long ee sound, rhyming with green. So yes, sheen is a real, recognized, and frequently used English word.