When was internet started?

It was around the time when ARPANET began to merge with NSFNet, that the term Internet originated, with "an internet" meaning any network using TCP/IP. "The Internet" came to mean a global and large network using TCP/IP, which at the time meant NSFNet and ARPANET. Previously "internet" and "internetwork" had been used interchangeably, and "internet protocol" had been used to refer to other networking systems such as Xerox Network Services.