Comment by ggm
Like a lot of people I think I hold a mental image of "jet" which is actually not helpful for a modern engine. All modern jets seem to have this massive rotational component, the turbine, and the fan outside the turbine chamber. so does a turboprop. And the basic propeller before that. Oh, the "fan" has more blades. Pshaw! a spitfire went from 3 blades to 5 across it's lifetime. post-spitfire engines had contra rotating props with many more blades. It can't just be about the NUMBER of blades can it?
So, there is the turbine. Is that directly coupled to the "fan" bit? If not, it's probably a turboprop, but even then I am unsure all visible fans on modern jets on the spool couple directly to the turbine.
The "jet" part is the combustion chamber. Everything else, you might as well consider turbines and propellers as "the same kind of thing" but then you're in a pub arguing which details make one a prop and the other a fan.
If you like Roger ramjet you're in the other kind of Jet: the one which is more like a rocket. Also, if you work in government service how are you passing the drug test with those proton energy pills?
Frank Whittle's biography is a great read. He had some hair raising moments. things OSHA would not be happy about.
> I am unsure all visible fans on modern jets on the spool couple directly to the turbine
They exist now [1][2]. The general term is geared turbofans.
If you want to mentally unfuck it a bit, the major variables are: combustion type (internal or turbine), gearing or not, ducting or not and bypass ratio. (Compression ratio and number of blades can come too.)
When one of these changes substantially, you get a change in engine type. When it changes a little bit, you get a blur.
[1] https://en.wikipedia.org/wiki/Pratt_%26_Whitney_PW1000G
[2] https://en.wikipedia.org/wiki/Rolls-Royce_Trent#UltraFan