Nobody knows anymore, it’s kind of feature size, but everyone defines feature differently!
It seems like transistor density (N per unit area) would be a more useful measurement.
Isn't that the logic behind the "fake" nanometer measurements? Let's say everyone is on "32nm", but you got a new process[1] that packs twice the number of transistors than everyone else, but with the same feature size. Essentially, your 32nm feature size process is equivalent to everyone else's 22nm feature size process. Are you going to advertise your new process as "32nm" which is the same as everyone else, or "22nm"?
I mean I'm no chip designer but surely they are using some crazy hacks like transistors that take up more space than the lines between them by being part of the substraight above and below the etched lines. And presumably they use interference/coherence to etch even finer details? There are probably about a million different techniques they use to pack in more transistors without making the process smaller.
0.235nm between atoms, 1/30th of 7nm. (Though, precisely what does the 7nm number measure?)