Spell-check your document

First, you need to enable the plugin:

You can configure the default spell-checking settings for new documents by going to the Menu ▸ Preferences ▸ Plugins ▸ Spell Checker ▸ Preferences.

To use the spell-checker, go to the Menu ▸ Tools.

If you activate the Highlight Misspelled Words option, the misspelled words will be underlined in red in the document. A right click on a misspelled word will show proposals.

The settings are remembered on a file-by-file basis: when you reopen a document, the chosen language is restored, as well as whether the misspelled words are highlighted in the text area.

gspell is used for the spell-checking in gedit. gspell uses Enchant, which in turn supports several backends such as Hunspell or Aspell for the dictionaries. The Aspell backend doesn't work well with gspell, Hunspell is preferred. If dictionaries for both Aspell and Hunspell are installed for the same language, by default Enchant prefers the Hunspell one.

If your language is not listed in gedit, install a dictionary for one of the supported Enchant backends (for most languages the best choice is to install an Hunspell dictionary).