For Developers‎ > ‎How-Tos‎ > ‎  Editing the spell checking
dictionaries  Each hunspell dictionary comes in two files.
The .dic file which is the list of words, and the .aff file
which is a list of rules and other options. You will normally
only need to add to the .dic file, but you may need to refer to
the .aff file for several things.  We maintain some additions to
the dictionary files which we keep in a separate file ending in
.dic_delta. Keeping the original unchanged allows us to more
easily pull updated versions from the dictionary maintainers.
Chromium actually reads an optimized format which uses the
suffix .bdic. This file is generated from the .aff, .dic, and
.dic_delta files using the convert_dict tool in the Chromium
project. All of these files are checked
into deps/third_party/hunspell_dictionaries/ in Subversion, and
checked out into src/third_party/hunspell_dictionaries when
syncing locally.  Encoding issues  The .dic and .aff files are
normally in the encoding most appropriate for that languag