Genus (InstanceTopic, 3)

From Hi.gher. Space

The genus of an object is equal to how many "holes" it has that fully pierce the object.

Lines always have a genus of zero. If a hole was created it would be split in half.

There are two types of holes that an object can have. Pockets are holes completely inside the object and cannot be seen by any outside viewer (unless the being viewing the object is in a higher dimension than the object itself). Ordinary holes are ones that can be seen from the outside, for example the hole in a torus. The only type of hole that can be placed inside a polygon is a pocket, as creating a normal hole would split the object in half.