More specifically in Euclidean geometry a point is a primitive notion upon which the geometry is built meaning that a point cannot be defined in terms of previously defined objects. It has no size only position. The interior of S is the complement of the closure of the complement of S.
Sometimes written as the letter O In three dimensions it is the point 0 0 0 where the x y and z axis cross.
Preserved property Under a transformation a property which if present in a preimage is present in the image. A plane is a 2-dimensional flat surface. More specifically in Euclidean geometry a point is a primitive notion upon which the geometry is built meaning that a point cannot be defined in terms of previously defined objects. In modern mathematics a point refers usually to an element of some set called a space.