Or a LAN. Could do a WAN which itself can be interconnected over a wide area. Usually by routing over the internet but you could use something like satellite uplink or miles of dedicated cables.
But the interconnection of multiple LANS and WANS is what would make an “internet”.
So maybe 2 universities joining their own networks would be moving towards a private “internet” but I think we’d still call that a private network or a WAN.
It’s interesting to consider where the definitions change.
It’s like how the earth bulges out at the equator.
The momentum pulls them out, gravity pulls it back. Similar thing at the solar and galactic planes.
They “bulge” relatively to the spin of the material over time and the clumps of material then forms planets along that general plane.
From the aboves video you can see this at 44seconds
https://www.youtube.com/watch?v=sCkhEu3lYNc&t=44s
And a relevant PBS Spacetime video
Why is the Earth Round and the Milky Way Flat? | Space Time | PBS Digital Studios
But the biggest reason is the way gasses form in space. As noted in the above video at the 8:45 mark. Gasses aren’t able to fall back into the center along their axis of spin because of their momentum. But the gassed above and below the plane can move towards the gathering material there by gravity and so it flattens out.
https://youtu.be/Aj6Kc1mvsdo?t=8m45s