n.能见度；可见性
Fog restricted visibility. 雾天能见度很低。
Dense fog is covering roads in the north and visibility is very poor. 浓雾笼罩了北部的公路，能见度很低。
The visibility of the lunar formations depends on their illumination by the sun. 月球结构的可见性取决于太阳对它们的照明。
n.看不见；隐形
n.[数]可除性；可约性
