A dot-file is generally any file whose name begins with a full stop.
In Unix-like operating systems, dot-file is synonymous with hidden file.
As a special case, dot-files whose names begin with ._ can be suspected as being AppleDouble companions of an ordinary file in the same directory.
In Classic Mac OS, there was a recommendation that dot-filenames were reserved for device drivers.
Also:
DOT is a plain text graph description language. DOT graphs are typically files with the file extension gv or dot. The extension gv is preferred to avoid confusion with the extension dot used by early (pre-2007) versions of Microsoft Word.
