The heavenly expanse spread out over the water surfaceThe heavenly expanse spread out over the water surface
Reflection of mountains in the lake surface winter dayReflection of mountains in the lake surface winter day
The surface of the lake against the background of snow-capped mountainsThe surface of the lake against the background of snow-capped mountains
The surface of the lake against the background of a very beautiful sunsetThe surface of the lake against the background of a very beautiful sunset
В математике: граница, отделяющая геометрическое тело от внешнего пространства. Наружная сторона чего-н..