Fall back to default language if translation missing

Nowdays there’s no need for using separate i18n gem, on plain Rails 3.0.6 and above (5.0 included) installation, fallbacks value can be one of the following:

# application.rb

# rails will fallback to config.i18n.default_locale translation
config.i18n.fallbacks = true

# rails will fallback to en, no matter what is set as config.i18n.default_locale
config.i18n.fallbacks = [:en]

# fallbacks value can also be a hash - a map of fallbacks if you will
# missing translations of es and fr languages will fallback to english
# missing translations in german will fallback to french ('de' => 'fr')
config.i18n.fallbacks = {'es' => 'en', 'fr' => 'en', 'de' => 'fr'}