LanguageTool is an Open Source style and grammar proofreading software for English, French, German, Polish, Dutch, Romanian, and a number of other languages - see the list of supported languages.
You can think of LanguageTool as a software to detect errors that a simple spell checker cannot detect, e.g. mixing up there/their, no/now etc. It can also detect some grammar mistakes. It does not include spell checking. LanguageTool will find errors for which a rule has been defined in its language-specific configuration files.
The LanguageTool plugin is included in OmegaT. It will be used automatically by OmegaT if also and I didn't do nothing in the picture above). When hovering the mouse over the underlined phrase, an explanation will appear.
is checked. The rules applied (if any) will depend on the source and target language of the project. When a rule is triggered, the corresponding phrase will be underlined in blue in the Editor (seeLanguageTool will not work properly if an old version is found in the /plugin folder. Remove LanguageTool from the /plugin folder before starting OmegaT.