A dictionary must be installed for your language. The installation is done by an extension as explained in this item. You must close LibreOffice completely, including the quick starter, in order for the new dictionary to be taken into account. The default dictionary for your language is installed.
Go to the Tools ▸ Options ▸ Language Settings ▸ Language ▸ language modules available menu, click the Edit button.
In the Language drop-down box, select Your_language, which must be preceded by the A icon (before version 5.X the icon contained an ABC).
In the Spelling module, a dictionary must be checked (by default Hunspell SpellChecker).
In the menu Tools ▸ Options ▸ Language Settings ▸ Language Options ▸ Check spelling as you type must be checked (this option is directly accessible in the Standard toolbar).
Check that the default language is your: in the Tools ▸ Options ▸ Language Settings ▸ Languages​​ ▸ Default language for documents ▸ Western, enter Your_language.
in Writer, display the Style and Formatting window with F11, in the Paragraph Styles, right click Standard then Modify.
In Impress or Draw, Format ▸ Character ▸ Font ▸ Language menu.
In the Tools ▸ Options ▸ Language Settings ▸ Languages ▸ Default language for documents ▸ Western menu, specify a language other than Yours.
Confirm and close LibreOffice completely, including the quick starter.
Restart LibreOffice and open the Tools ▸ Options ▸ Language Settings ▸ Languages​​ ▸ Default language for documents ▸ Western, enter Your_language.
This page was last edited 21:48:12, 2018-05-08 by Dennis Roczek. Based on work by Lera Goncharuk, The Document Foundation Wiki user Pietro and others.