| A | B |
| Closed | Does contain it's boundary points |
| Open | Does not contain it's boundary points |
| Convex | All lines stay within the boundary |
| Set | Any related group of objects |
| Star | Each machine knows where the center is |
| Ring | Each machine connected to the one before and after |
| Bus | Simplest topology |
| Four Color Theorem | Used in making 19th century maps |