What languages does Siri understand?
Siri currently understands English (United States, United Kingdom, Australia), French (France) and German (Germany). Apple plans to add Chinese, Korean, Italian, and Spanish in 2012.
Updating to iOS 5.1 adds Japanese support for Siri.iOS 6 adds: Italian, Mandarin, Spanish, Cantonese, Swiss French, Swiss German, Chinese
iOS 8.3 adds: Russian, Danish, Dutch, Portuguese, Swedish, Thai, Turkish, and English for India