"Internet" means a rule of communication (called TCP/IP), or a system where this rule is realized.
Anology : Rule of the road, or a system of roads where the rule works"
The rule of communication called "TCP/IP" defines "Internet", as the rule of the road difines "road".
In particular, there is not such a thing as "Internet circuit".
If you use a public telephone line or a radio, it is an "Internet circuit" in that time.
Internet bears a resemblance to the road network.
"Road"
"Internet"
How to use defines "road"
How to use : "Rule of the road"
How to use defines "Internet"
How to use : "TCP/IP protocol"
"Rule of the road" and "TCP/IP protocol" is alike in the following sense, too.
"Rule for letting many people use a thing""
Dividing a thing into small packets and sending them one by one, so that the road should not be owned by a single user ("Packet Transferring").
