眼(eye)
接收光线和视觉影像的器官。非成像眼或方向眼见於蠕虫、软体动物、刺胞动物、棘皮动物和其他无脊椎动物，成像眼见於特定的软体动物、大部分节肢动物和几乎全部脊椎动物。节肢动物拥有独特的复眼（compound eye），导致它们看见多重影像而在脑中将各部分加以整合。鱼等较低级的脊椎动物在头部两侧有眼，能对环境有最大视界，但产生二个分立的视野。在掠夺性鸟类及哺乳动物中，双眼视觉是重要的。眼睛位置的演化变迁让二个视野有较大的重叠，导致较高级哺乳动物有平行的直接视线。人眼大致为球形。光线通过其中透明的前部，刺激了视网膜（彩色影像下呈圆锥形，微光黑白视觉下呈长条形）上的接收细胞，进而经由视神经把脉冲送到大脑。视觉疾病包括近视（nearsightedness）、远视（farsightedness）、散光（astigmatism，可藉眼镜〔eyeglass〕或隐形眼镜〔contact lens〕加以矫正）、色盲（color blindness）、夜盲（night blindness）。其他的视觉疾病（包括视网膜剥离〔detached retina〕和青光眼〔glaucoma〕）会造成视野缺损（visual-field defect）或致盲（blindness）。参阅ophthalmology和photoreception
English version：
eye
Organ that receives light and visual images. Non-image forming, or direction, eyes are found among worms, mollusks, cnidarians, echinoderms, and other invertebrates; image-forming eyes are found in certain mollusks, most arthropods, and nearly all vertebrates. Arthropods are unique in possessing a compound eye, which results in their seeing a multiple image that is partially integrated in the brain. Lower vertebrates such as fish have eyes on either side of the head, allowing a maximum view of the surroundings but producing two separate fields of vision. In predatory birds and mammals, binocular vision became more important. Evolutionary changes in the placement of the eyes permitted a larger overlap of the two visual fields, resulting in the higher mammals in a parallel line of direct sight. The human eye is roughly spherical. Light passes through its transparent front and stimulates receptor cells on the retina (cones for color vision, rods for black-and-white vision in faint light), which in turn send impulses through the optic nerve to the brain. Vision disorders include near- and farsightedness and astigmatism (correctable with eyeglasses or contact lenses), color blindness, and night blindness. Other eye disorders (including detached retina and glaucoma) can cause visual-field defects or blindness. See also ophthalmology, photoreception.