What is the Internet?

The Internet is a global system of interconnected computer networks that interchange data by packet switching using the standardized Internet Protocol Suite (TCP/IP).

Wikipedia

The Internet is an open and universal network of networks, defined by TCP/IP protocol standards and operating as a decentralized and highly scalable matrix of systems spanning the entire planet. Like the Universe of which it is a microcosm, the Internet has no definite limits or boundaries and is subject to continual expansion and evolution.

The name Internet is a proper noun and is derived from the term “internetworking” and has always only referred to this universal network. The generic usage of the term internet (and its plural form, internets) has no known precedent and its use in this context is totally incorrect and confusing. No mentally competent and educated human being would ever use the generic lowercase term “internet” to refer to the universal Internet.