The Free On-line Dictionary of Computing (30 December 2018):

parent process

    The Unix process that created one or
   more other processes.

   Every process except process 0 is created when another process
   executes the fork system call.  The process that invoked
   fork is the parent process, and the newly created process is
   the child process.  Every process has one parent process,
   but can have many child processes.

   The kernel identifies each process by its process
   identifier (PID).  Process 0 is a special process that is
   created when the system boots; after forking a child process
   (process 1), process 0 becomes the swapper process.  Process
   1, known as init, is the ancestor of every other process in
   the system and enjoys a special relationship with them.

   (1997-12-03)