A polymer with only one starting point and ending point is called a linear polymer.

Here's why:

* Linear polymers consist of monomers (the building blocks) linked together in a single chain. This chain has a defined beginning and end.

* Branched polymers have side chains branching off the main chain, resulting in multiple starting and ending points.

* Cross-linked polymers have multiple chains connected by chemical bonds, forming a network structure with many interconnected starting and ending points.

Examples of linear polymers:

* Polyethylene (PE)

* Polypropylene (PP)

* Polyvinyl chloride (PVC)

* Nylon

* Polyester

Let me know if you'd like to know more about different polymer structures!