Sunglasses are the dark eye glasses you wear on bright days. Tinted lenses that cut the glare.
The word is always plural, so you buy a pair of sunglasses. British informal speech says sunnies and American says shades. They are genuinely protective rather than decorative, since ultraviolet light damages eyes over time, which is why the label matters more than the price. Polarised lenses cut reflection off water and roads. Wearing them indoors remains one of the most reliable signals of self-regard available.
1nounsunglassesGlasses with darkened lenses worn to protect the eyes from bright light.
“He pushed his sunglasses up onto his head.”
Also accepted in games: shades
From sun + glasses.
Etymology from Wiktionary, CC BY-SA