Good bye OS X and hello macOS

At WWDC 2016, Apple has announced the next version of its Mac operating system: Sierra. OS X is ditched now and the new operating system will simply be called "macOS." 

macOS Sierra includes some impressive new capabilities, including Siri, an automatic unlocking feature, universal Clipboard support, new iCloud integration, Apple Pay for the web, and more.

http://www.apple.com/macos/sierra-preview/

http://www.macrumors.com/roundup/macos-sierra/