Set Fallback Language
Fallback language is the parent language from which any given language inherits data.
When you add a language in the stack, you are prompted to set the fallback language.
Note: You can only set a language as the fallback language if that language is already added in your stack.
If you want to update the fallback language of an existing language, follow the steps mentioned in the Update Fallback Language article.
API Reference
To set a fallback language for a language via API request, refer to the Set a fallback language API request.