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General information
This is libvoikko, library of free natural language processing tools
The library is written in C++. The library supports multiple backends:
- VFST: Finite state transducer format used for Finnish morphology
and as an experimental language independent backend.
- HFST: Supports ZHFST speller archives for various languages.
- Experimental Lttoolbox backend.
Libvoikko provides spell checking, hyphenation, grammar checking and
morphological analysis for Finnish language. Only spell checking is
supported for other languages through HFST backend.
Libvoikko aims to provide support for
languages that are not well served by Hunspell or other existing free
linguistic tools. This can be done because we do not care about
compatibility with legacy dictionary formats and we support only actively
maintained languages. Pushing new features to Hunspell where
they would need to be maintained essentially indefinitely should not
be done until we have gained enough experience to know which solutions
work in the real world.
The core library and backends that are enabled by default are available
under MPL 1.1 / GPL 2+ / LGPL 2.1+ tri-license.
Lttoolbox backend is available only under GPL version 2 or later.
Backend License
VFST MPL 1.1 / GPL 2+ / LGPL 2.1+
HFST MPL 1.1 / GPL 2+ / LGPL 2.1+ (Apache v2 dependency)
Lttoolbox GPL 2+ (GPL 2+ backend and GPL 2+ dependency)
- Spell checking using compound word and derivation rule system that is
largely compatible with widely used proprietary Finnish spell checkers
such as the one used in MS Word.
- Spelling suggestions that are generated to catch most probable typing
- Special spelling suggestion mode that can be used to correct errors
produced by optical character recognition software.
- Hyphenator with compound hyphenation based on morphological analysis.
- Various options to tune spell checking and hyphenation for different
purposes and applications.
- Grammar checking and context sensitive spell checking using paragraph
based API.
- String tokenizer and sentence splitter.
- Morphological analyzer.
- All functionality is made available through C, Python, Java and .Net APIs.
Documentation for using the library can be found from header file voikko.h.
Build requirements
C++ compiler (GCC or clang) and Python (version 3.0 or later)
must be available in order to build this library. Pkg-config is needed
for build configuration.
Java API is designed to be built as a Maven project. No autotools or Ant
based build system is available yet.
When building from Git checkout you will need autoconf, automake and pkg-config
to generate the configure script.
Build configuration
See ./configure --help for a list of available configuration options.
The default configuration enables those backends that are recommended for
typical use: VFST for Finnish and HFST for other languages.
Disabling the default backends is safe if you do not need to use the dictionary
formats supported by them.
You can also enable certain experimental backends. Such configurations will
not necessarily work with all dictionaries and the dictionary
formats may change without notice. Thus these options should generally be used
in developer builds only. If you need to use them in a released build we
strongly recommend that you disable external dictionary loading with
--disable-extdicts and supply compatible dictionaries along with the library.
Runtime requirements
For dictionary format 3 (HFST backend):
Any valid ZHFST speller with file suffix .zhfst can be used. The name
of the file is not significant.
For dictionary format 5 (Finnish VFST backend):
Valid VFST dictionaries can be built from voikko-fi version 2.0 or later.
Python bindings work with Python version 2.7 or later. No conversion is needed
in order to use the module with Python 3.
Search order for dictionary files
A set of available dictionary variants is built by examining the contents of the
following directories. If a variant exists in more than one location, the first
occurrence is used and the rest are ignored.
1) Path given as the last argument to voikkoInit.
2) Path specified by the environment variable VOIKKO_DICTIONARY_PATH, if the
variable is set in the environment of the process initializing the library.
3) Only on platforms with Unix home directories (Linux, BSD and Mac OS X):
a) from directory $HOME/.voikko
i) Only on Mac OS X: from directory $HOME/Library/Spelling/voikko
b) from directory /etc/voikko
4) Only on Windows:
a) Directory specified by the registry key
b) User specific local application data directory, usually
C:\Documents and Settings\$username\Local Settings\Application Data\voikko
c) Directory specified by the registry key
5) Path specified at compile time using --with-dictionary-path
In 2), 4) and 5) it is possible to specify multiple locations by separating them with
the OS specific paths separator (; on Windows, : on other operating systems).
The locations will be processed in the listed order.
Locations 2) to 5) are not used if the library is configured with --disable-external-dicts
Using this option is recommended if dictionaries are distributed with the library
and support for experimental dictionary formats is enabled.
To all of the paths above additional path component "/2" is appended at the end.
This corresponds to the dictionary version and allows multiple versions of the same
dictionary to be installed simultaneously. The version number may be other than "2".
Dictionaries and language variants are searched from files or subdirectories using
the rules that are specific to each format version.
One of the dictionaries is chosen to be the default dictionary by trying the
following rules:
1) If one of the subdirectories in the main directory paths described above has
name "mor-default", the default dictionary will be the variant that is found
from that directory. Note that this does not affect the actual decision about
the dictionary instance used to provide the variant. If, for example, there is
a directory $HOME/.voikko/2/mor-a containing variant "a" and a directory
/etc/voikko/2/mor-default containing variant "a", the variant "a" will become the
default but it will still be provided by $HOME/.voikko/2/mor-a.
2) If no default is specified, variant "standard" is used as the default.
3) If variant "standard" is not available, the variant with the name that comes
first in alphabetical order is selected as the default.
Selection of the variant to use
The dictionary variant to be used is determined using the following rules, starting
from rule 1:
1) If the parameter 'langcode' given to functions voikko_init or voikko_init_with_path
is NULL, no dictionary will be loaded. The behaviour of the library after such
initialization is currently undefined.
2) If the parameter 'langcode' given to functions voikko_init or voikko_init_with_path
is something else than "", "default" or "fi_FI", variant with that name is loaded.
If the variant is not available, an error is returned.
3) If environment variable VOIKKO_DICTIONARY is defined, its value is used as the
name of the dictionary variant to load. If the variant is not available, an error
is returned.
4) Finally, the default variant is loaded. If no dictionary variants are available,
an error is returned.
2006 - 2021 Harri Pitkänen (
* Maintainer, core library developer.
2006 Nemanja Trifunovic
* Author of UTF8 utility module.
2011-2012 Teemu Likonen <>
* Author of the Common Lisp interface.