Grammar and spell checker
A checker is a type of software that enables automatic detection of misspelled words, and sometimes ungrammatical phrases too.
Spell checking can be considered as the basis for checking softwares. Spell checking capabilities can be found among other things as an add-on for Firefox (browser), as an add-on for (Pidgin) (instant messaging client) or within an email service such as Gmail. Spell checking usually comes with a closest word suggestion feature. A spell checker alone does not detect anything wrong with correctly spelled words placed next to one another when they don't make sense, as long as they are spelled correctly.
Creating a grammar checker is much more complex than creating a spell checker. Not only does it require a word list like a spell checker does, but it also requires those words to be tagged properly and a set of grammar rules to describe the way words should be placed in a sentence.
A common issue with spell and grammar checkers is noise. For instance, some French grammar checkers report "Nous nous" as a mistake. However, this phrase is common in French ("Nous nous sommes lavés": "We washed ourselves"). This alert is triggered as a noise for the doublet-detecting rule.
Silence is another common issue with grammar checking. This is caused by the extent of rules to be created to list all possible mistakes. Agreement rules are usually the first to be covered with grammar checking. However, grammar mistakes are just one of part of mistakes that can be made. Use of substandard English is also possible in other ways and can concern regionalisms, dated phrases, offensive phrases, slang, etc.
- LanguageTool, an open source grammar checker with mature support for English and limited support for other languages that can be used as a stand-alone application
- SpellCheck Plus, an online proprietary grammar checker (although the name does not suggest it) which can be tried for free, but with limitations