I recently worked on a Rails project, which had parts of pages in different languages. That may be a problem if you have already translated their entire text to all required languages. You can even be tempted to hardcode parts of the text into other languages. Fortunately, there is an elegant way to solve that problem, just wrap parts of template or partials into blocks with desired locale, like this:

<% I18n.with_locale('en') do %>
  ...part of your template
  <%= render partial: 'some/partial' %>
<% end %>


Suppose, there is a template with only header and two paragraphs.

<h1><%= t('my_great_header') %></h1>

<p><%= t('first_paragraph') %></p>

<p><%= t('second_paragraph') %></p>

And locale in English and French for that template.

# in config/locales/en.yml
  my_great_header: "My English great header"
  first_paragraph: "First English paragraph"
  second_paragraph: "Second English paragraph"

# in config/locales/fr.yml
  my_great_header: "My French great header"
  first_paragraph: "First French paragraph"
  second_paragraph: "Second French paragraph"

And client wants first paragraph to always be in English.

Just wrap first paragraph in block with locale 'en, like this:

<h1><%= t('my_great_header') %></h1>

<% I18n.with_locale('en') do %>
  <p><%= t('first_paragraph') %></p>
<% end %>
<p><%= t('second_paragraph') %></p>

and when you switch language to Franch result will be:

My French great header

First English paragraph

Second French paragraph

I hope that this helps. Have a nice day.