Trees in autumn attire, reflected in the surface of the lake in clear and windless weatherTrees in autumn attire, reflected in the surface of the lake in clear and windless weather
A lonely island on the background of the sea surfaceA lonely island on the background of the sea surface
A lonely boat on the blue surface of the sea under white cloudsA lonely boat on the blue surface of the sea under white clouds
Night lights of the metropolis on the background of the water surfaceNight lights of the metropolis on the background of the water surface
В математике: граница, отделяющая геометрическое тело от внешнего пространства. Наружная сторона чего-н..