We currently have quite a few tags about filament:
I feel like we need to clean these up and make clear what we'll use each tag for.
I see a form of hierarchy that could be used.
Depending on the question a higher level tag could be used or a more specific one for specific problems (or both tags even).
Feel free to edit to add more types
I bump this and propose the radical method:
The difference between thermoplastic-filament and plastic-filament in use is nonexistant and both are pretty much identical to filament in the current use - it is rather random which one gets used, in many cases more than one is used.
There is no filament that can be used in 3D printing that is not a thermoplastic, as the method to re-shape the filament via heat demands a thermoplastic.
While there are clearly more plastics than thermoplastics, non thermoplastic plastics are not useable for 3D printing unless you would design a whole printer to use for example an UV-curing resin delivered to the workpiece via a needle - which makes this a non-FDM printer.