Siri is a voice-controlled virtual personal assistant, and it's built right into your Apple Watch.
On the iPhone, Siri is a secondary interface used when talking is more convenient than tapping. On the Apple Watch, Siri is a primary interface. It's not just the only way to enter text and a much more convenient way to initiate actions, but it's also the only way to search web services like Wikipedia, Wolfram Alpha, and Bing images. Talking to your watch might seem like sci-fi, but Siri makes it a reality.
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