Cortana is one of the most important feature of the recently announced Windows Phone 8.1 OS. It is a virtual assistant for Windows Phones which competes with Google Now on Android and Siri on iOS. Cortana is still under development and is only available for windows phone users in the United States. The name Cortana comes from the artificial-intelligence character found in Microsoft’s HALO video games. Cortana is expected to be released for all other countries in the next year. But if you don’t want to wait until next year, here is little trick to activate Cortana on Windows Phone 8.1
1. Go to settings>language+region and change your language to English (United States) and Country/Region to United States.
2. Now, also make sure that you have activated speech language for English (United States). Download this language pack if its not available.
3. After performing above Steps ,restart your phone once to activate Cortana.
Note : Because it is still under beta, if you encounter any problem while using cortana , then you can deactivate Cortana by changing phone settings to your region.