""regular files" is a pretty precise, standard UNIXy term to mean file system objects that are not directories, symlinks, sockets, (character or block) special device files or named pipes. Anything that satisfies `test -f` or the find(1) condition `-type f`, which is implemented using the `S_ISREG` macro mentioned in stat(2). Now, if this term is "clear" or not is another issue, and is, of course, going to be based on familiarity and what else is covered during the training." - Andy Bakun