wp language core install
Installs a given language.
Downloads the language pack from WordPress.org. Find your language code at: https://translate.wordpress.org/
wp language core install <language>... [--activate]
Examples
# Install the Brazilian Portuguese language.
$ wp language core install pt_BR
Downloading translation from https://downloads.wordpress.org/translation/core/6.5/pt_BR.zip...
Unpacking the update...
Installing the latest version...
Removing the old version of the translation...
Translation updated successfully.
Language 'pt_BR' installed.
Success: Installed 1 of 1 languages.