抄送(copy)与副本送(carbon copy)的区别

In e-mail, a carbon copy (abbreviated "cc," and sometimes "fcc" for "first carbon copy") is a copy of a note sent to an addressee other than the main addressee.

As for C, I haven't seen before.

Abbr. ccA duplicate, as of a letter, made by using carbon paper.
缩写 cc副本：用复写纸写成复写本，如一封信的复写本
A person or thing that closely resembles another.
极其相似的人或物

所以cc=c,但是有cc与bcc的区别bcc=blind carbon copy