Hi,

You can't delete a language if:

    It's the default system language.

    It's used by any user.

    It's used in translations (like product names or website text).

    It's a core Odoo language (like en_US).

  How to delete a language

    Check Users:Make sure no one is using that language (Settings > Users > check Language).

    Change Default Language (if needed):Switch to another default language (like en_US).

    Delete Translations (optional):Go to Settings > Translations > Translated Terms, filter by that language, and delete if needed.

    Delete the Language:Go to Settings > Translations > Languages, open it, and click Delete.

Hope it helps