What is the number called that is used to identify a process?

Proc Num is not a defined or standard term in operating system terminology for identifying processes.

PIN stands for Personal Identification Number and is an authentication concept, not an OS process identifier.

Process Entry describes a data structure or record in a process table, not the numeric identifier used to reference a specific process.

The operating system kernel assigns each process a unique integer called a Process ID (PID) at creation time. The PID is used by the OS scheduler, system calls (such as kill and wait), and utilities like ps and top to reference and manage individual processes. It is the standard term defined in POSIX and used across all Unix-like operating systems.