Open morphology for Finnish
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Omorfi–Open morphology of Finnish

This is a free/libre open source morphology of Finnish: a database, tools and APIs. This package is licenced under GNU GPL version 3, but not necessarily later. Licence can also be found in the COPYING file in the root directory of this package. Other licences are possible by all the authors named in the AUTHORS file.

Omorfi has been used for a number of tasks:

  • morphological analysis
  • morphological segmentation
  • spell-checking and correction
  • information retrieval
  • ontologies
  • statistical machine translation
  • rule-based machine translation
  • language modeling
  • tokenisation and sentence boundary detection
  • stemming, lemmatisation and shallow morph analysis

The lexical data of omorfi has been acquired from various sources with different original licences. The dictionaries used in omorfi are Nykysuomen sanalista (LGPL), Joukahainen (GPL) and FinnWordNet (Princeton Wordnet licence / GPL; relicenced with kind permission from University of Helsinki), and Finnish Wiktionary (Creative Commons Attribution–ShareAlike). Some words have also been collected by omorfi developers and contributors and are GPLv3 like the rest of the package.

These are the obligatory stamps of the day:

Build Status

Downloading and further information

→ See also: Release policy

Omorfi is currently hosted at github. Omorfi's github repository contain most of the important information about omorfi: version control system for source codes, bug tracker for reporting bugs, and the stable releases as convenient packages. Omorfi's gh-pages site contain further information not found in this README.


Before you start: Apertium wiki has installation information for most dependencies on their Apertium installation pages, look at section called pre-requisites, e.g., if you are looking to build omorfi on Ubuntu, go to: Pre-requisites for Ubuntu.

Compilation of the morphological analyser, generation, lemmatisation or spell-checking requires HFST tools or compatible installed. For use, you will need the python bindings too, and a relatively recent version of python 3. Of course standard GNU build tools are needed as well. You should have versions no older than one or two years. The build is not guaranteed to work at all with all ancient versions of GNU build tools, HFST or python. The versions that should work are as follows:

  • hfst-3.8 or greater, with python bindings
  • python-3.2 or greater, with hfst python bindings available
  • GNU autoconf-2.64 and automake-1.12

The use of certain automata also requires additional tools:

  • hfst-ospell-0.2.0 or greater needed for spell-checking

APIs require:

  • Python 3.2 for python API
  • Java 7 for Java API
  • Bash 3, coreutils for bash API
  • The C++ API uses C++-11, this is basically available on all modern platforms.


Installation uses standard autotools system:

./configure && make && make install

The compiling may take forever or longer, depending on the hardware and settings used. You should be prepared with at least 4 gigs of RAM, however, it is possible to compile a limited vocabulary system with less. This is a limitation of the HFST system used to compile the language models, and it is only present at compile time, the final models use perhaps up to hundreds of megabytes in memory.

If configure cannot find HFST tools, you must tell it where to find them:

./configure --with-hfst=${HFSTPATH}

Autotools system supports installation to e.g. home directory:

./configure --prefix=${HOME}

With git version you must create the necessary autotools files in the host system once, after initial checkout:


For further instructions, see INSTALL, the GNU standard install instructions for autotools systems.

There are a number of options that you can pass to configure script. The default configuration leaves lots of features out to speed up the process, for a full listing:

./configure --help

Some of the features that build more automata double the time required to compile and the space used by the automata (approximately). Some features are to enable or disable the API bindings for Java or other languages. The configure script displays the current setup in the end:

* Analysers: yes
    * OMOR yes (flags: --omor-props   --omor-sem)
    * FTB3.1 no
    * apertium no
    * giella: no
    * labeled segmenter: no
* Limits:
    * tiny lexicons: 
    * big tests: 
* Applications
    * Voikko speller: yes
    * segmenter: no
    * lemmatiser: no
    * hyphenators: no
* Clusters
    * run tests on PBS cluster: false → mailto: no
    * run tests on SLURM cluster: false → mailto: no

For fully usable system you may want to turn the applications on.


All of the scripts can be invoked with -h to see options. Most take file (list) as input or just read standard input, in plain text format. Some programs may require specific automata or language models.

  1. analyse text and disambiguate using VISL CG-3
  2. analyse plain text into ambiguous word-form lists
  3. spell-check and correct word-forms one per line
  4. morphologically segment word-forms one per line
  5. omorfi-conllu.bash: analyse text and print CONLL-U format output (Universal Dependencies)
  6. omorfi-freq-evals.bash: analyse text and print out frequency list and coverage
  7. omorfi-ftb3.bash: analyse text and print out FTB3.1 formatted output (FinnTreeBank, CONLL-X compatible)
  8. omorfi-factorise.bash: analyse text and print out Moses factored format
  9. omorfi-vislcg.bash: analyse text and print out VISL CG 3 output
  10. analyse pre-tokenised word-forms one per line (unlike other functions, this takes word list and not text input)
  11. generate word-forms from omor descriptions (unlike other functions, takes analysis list as input)

Some functions come with lower-level interface, where you have to take care of full pipeline manually but have more control over parametres:

  • format raw text into tokens (words and puncts).
  • analyse and generate CONLL-U formatted data (Universal Dependencies) format
  • analyse raw texts into VISL CG 3 format
  • morphologically segment word-forms one per line
  • analyse raw texts into moses factored format
  • analyse frequency lists and generate coverage
  • analyse and generate FTB3 (CONLL-X) format

For further examples please refer to:

Programming APIs

Omorfi can be used via very simple programming APIs, the design is detailed in omorfi API design

Python API is in Omorfi class under omorfi.omorfi (may change in the future), and requires HFST python bindings.

Java API is in com.github.flammie.omorfi.Omorfi and uses hfst-optimized-lookup-java package (bundled or in classpath).

C++ API is in omorfi::Omorfi class and uses hfst API.

Bash "API" is in omorfi.bash and uses hfst tools and GNU coreutils.

Using binary models

The compiled dictionaries are saved in binary files that can be handled with various tools. Most of them are in HFST optimised format and can be used with HFST tools. The CG3 binary is for VISL CG 3, the ZHFST file is compatible with hfst-ospell and voikko, and the tsv file is the lexical database in TSV format.

For usage examples see our usage examples. The binaries are installed in $prefix/share:

master.tsv                   omorfi-omor.analyse.hfst
omorfi.accept.hfst           omorfi-omor.generate.hfst
omorfi.analyse.hfst          omorfi-omor_recased.analyse.hfst
omorfi.cg3bin                omorfi_recased.analyse.hfst
omorfi.describe.hfst         omorfi_recased.describe.hfst
omorfi-ftb3.analyse.hfst     omorfi.tokenise.hfst
omorfi-ftb3.generate.hfst    omorfi.tokenise.pmatchfst
omorfi.generate.hfst         omorfi.tokenise.pmatchfst.debug1
omorfi-giella.analyse.hfst   omorfi.tokenise.pmatchfst.debug2
omorfi-giella.generate.hfst  speller-omorfi.zhfst

The actual listing depends on features and tagsets selected in the configuration phase.


For full descriptions and archived problems, see: Troubleshooting in github pages

hfst-lexc: Unknown option

Update HFST.

ImportError (or other Python problems)

In order for python scripts to work you need to install them to same prefix as python, or define PYTHONPATH, e.g. export PYTHONPATH=/usr/local/lib/python3.4/site-packages/

Processing text gets stuck / takes long

This can easily happen for legit reasons. It can be reduced by filtering overlong tokens out. Or processing texts in smaller pieces.

Make gets killed

Get more RAM or swap space.


Omorfi code and data are free and libre open source, modifiable and redistributable by anyone. IRC channel #omorfi on Freenode is particularly good for immediate discussion about contributions. Any data or code contributed must be compatible with our licencing policy, i.e. GNU compatible free licence. In the github, you may use the "fork this project" button to contribute, read github's documentation for more information about this work-flow.

We are currently using git-flow, but feel free to just send pull-requests as you find comfortable and we'll sort it out.

Coding standards

Python code should pass the flake8 style checker and imports should be sorted in accordance with isort. Ideally, you should integrate these into your editor, the development environment section of the python guide has instructions for a few editors. In addition, you can install a pre-commit hook to run the checks like so:

$ pip install pre-commit
$ pre-commit install

I (Flammie) also recommend syntastic, e.g. I use vim-syntastic