I also use the terms WAN and LAN, but please note the singularity of those terms. A Wide Area Network is only only network, not two. When you link two WANs, you have created an internet. It is easier to see in times past when, in the Department of Defense, certain branches had tied together their LANs and WANs, but did not tie them into the larger (growing) Internet. They did, however, have an internet (connecting their various networks). It couldn't properly be called a WAN or LAN because it was many WANs and LANs tied together. (In another aside, a LAN or WAN will have a central point where the network is administered; networks tying together multiple LANs and WANs don't have a single centralized control system.)

Again, I reiterate that most people may be unfamiliar with this kind of usage because many work with only the Internet and not with *independent internets. But I assure you, they exist.