Simple interest is calculated per year and it depends on the rate of interest. The rate is usually defined per annum ( same as per year ).
The volume of a cylinder is defined as the number of cubic units that will exactly fill the cylinder.
A sphere does not have any vertices or edges like other solid objects. It has only one surface. There are many examples of spheres - ball, marbles etc.
The volume of a cone is defined as the number of cubic units that will exactly fill the cone.