Supplement and letters What does it mean for journal to be "letters journal" and "supplement journal"? For example, Nuovo Cimento (https://en.m.wikipedia.org/wiki/Nuovo_Cimento) journal has this distinction.

Is "letter" a synonymum for "note"?
Letters are supposed to be short articles with innovative content, easy to communicate for the general scientific community.

From the Physical Review Letters website:


  It publishes short, high quality reports of significant and notable
  results in the full arc of fundamental and interdisciplinary physics
  research.


I've never heard about that another definition, seems like it is specific from the Nuovo Cimento journal. I would think that it publishes long articles with exhaustive detailed technical/theoretical reports.