What's the second?

Hindi/Urdu
Ironically, Hindi and Urdu are essentially the same language. In Pakistan, Hindi is modified and written in Arabic script, whereas in India, it is written in the Devanagari script and called Hindi. Combined, 600 million human beings speak Hindi. While every expert would assert that India's population will surpass China's, chances are that there will always be more Mandarin-speaking people because English is widely spoken in India, but not in China.


Source
http://www.askmen.com/toys/top_10/45_top_10_list.html