LanguageTool is an open source natural language processing tool that helps users detect and correct writing errors in various languages. It is designed to detect and correct spelling, grammar, and other common errors found in written text. It can be used as a stand-alone application or as an add-on for popular word processors, such as Microsoft Word and OpenOffice.org. LanguageTool supports over 20 languages, including English, Spanish, French, German, Dutch, Chinese, and many others. The tool can be used to check documents for accuracy and consistency, as well as to detect and correct errors that may have been overlooked. Additionally, LanguageTool can be used to detect and correct repeating words, typos, incorrect capitalization, and incorrect punctuation.
Grammarian PRO2 is by far the most accurate grammar check available. PRO2 works in the original document or in e-mail, without manual copy/paste.