レンズ

1870-71 is an early printed point for レンズ: Seisenban Nihon Kokugo Daijiten cites Nakamura Masanao's Saigoku Risshihen. The listed source languages are English and Dutch lens. The deeper source is Latin lens, “lentil,” because early optical lenses had a lentil-like convex shape. Japanese adopted レンズ in modern science and optics, a field already shaped by Dutch learning and later English technical vocabulary. Dictionaries define 凸レンズ and 凹レンズ, and the word spread to glasses, microscopes, cameras, and the eye's crystalline lens. Related terms include 眼鏡, 顕微鏡, カメラ, 水晶体, and レンズ豆. In modern Japanese, レンズ covers optical parts in cameras, eyeglasses, microscopes, and contact lenses. It does not take an English plural ending, so one lens and several lenses can both be レンズ. English lens and Dutch lens look the same, but Japanese separates the bean as レンズ豆. Example: カメラのレンズを替える.