Provider-aggregatable address space

Provider-aggregatable address space (PA) is a block of IP addresses assigned by a regional Internet registry to an Internet service provider which can be aggregated into a single route advertisement for improved Internet routing efficiency. Unlike provider-independent address space, the end-user of address blocks within a provider-supplied space cannot reuse the addresses if they change up-stream connectivity providers.

Source: Wikipedia — Provider-aggregatable address space (CC BY-SA 4.0)