Apple shortened the name to 'OS X' in 2011 and then changed it to 'macOS' in 2016 to align with the branding of Apple's other operating systems, iOS, watchOS, and tvOS. The derivatives of macOS are Apple's other operating systems: iOS, iPadOS, watchOS, tvOS, and audioOS.Ī prominent part of macOS's original brand identity was the use of Roman numeral X, pronounced 'ten', as well as code naming each release after species of big cats, or places within California. All releases from Mac OS X Leopard onward (except for OS X Lion) are UNIX 03 certified. The first desktop version, Mac OS X 10.0, was released on March 24, 2001. Its underlying architecture came from NeXT's NeXTSTEP, as a result of Apple's acquisition of NeXT, which also brought Steve Jobs back to Apple. Mac OS X succeeded classic Mac OS, a Macintosh operating system from 1984 to 2001. Within the market of desktop and laptop computers, it is the second most widely used desktop OS, after Microsoft Windows and ahead of all Linux distributions, including ChromeOS. It is the primary operating system for Apple's Mac computers. MacOS ( / ˌ m æ k oʊ ˈ ɛ s/ ), originally Mac OS X, previously shortened as OS X, is an operating system developed and marketed by Apple Inc.