I was wondering why they used the term "sub-terahertz" (isn't basically the entire RF spectrum "sub-terahertz"?), and it seems to refer to the ~75-300ghz range

I was wondering why they used the term "sub-terahertz" (isn't basically the entire RF spectrum "sub-terahertz"?), and it seems to refer to the ~75-300ghz range [0][1], including the W and D bands. While looking into this, I learned that terahertz frequencies are called THF or "tremendously high frequency"[2], which I thought was pretty funny. Pretty used to HF, VHF, UHF etc. but never heard of "THF" until now! [0] https://www.rfwireless-world.com/Terminology/Sub-THz-Bands-and-Frequencies.html https://www.rfwireless-world.com/Terminology/Sub-THz-Bands-a... [1] http://www.brave-beyond5g.com/index.php/sub-thz/ http://www.brave-beyond5g.com/index.php/sub-thz/ [2] https://books.google.ca/books?id=K9N1TVhf82YC&pg=PA7&redir_esc=y#v=onepage&q&f=false https://books.google.ca/books?id=K9N1TVhf82YC&pg=PA7&redir_e...