Title

# config/locales/en.yml
en:
  welcome: "Welcome to %{app_name}"
  items:
    one: "%{count} item"
    other: "%{count} items"

# app/controllers/home_controller.rb
class HomeController < ApplicationController
  def index
    @welcome = t('welcome', app_name: 'My App')
    @items = t('items', count: 5)
  end
end

# app/views/home/index.html.erb
<h1><%= @welcome %></h1>
<p><%= @items %></p>