The first desktop version, Mac OS X 10.0, was released in March 2001, with its first update, 10.1, arriving later that year. The "X" in Mac OS X and OS X is the Roman numeral for the number 10 and is pronounced as such. The X was a prominent part of the operating system's brand identity and marketing in its early years, but gradually receded in prominence since the release of Snow Leopard in 2009. Apple began naming its releases after big cats, which lasted until OS X 10.8 Mountain Lion. Since OS X 10.9 Mavericks, releases have been named after locations in California. Apple shortened the name to "OS X" in 2012 and then changed it to "macOS" in 2016, adopting the nomenclature that they were using for their other operating systems, iOS, watchOS, and tvOS. With Big Sur, Apple advanced the macOS major version number for the first time, changing it to 11 for Big Sur from the 10 used for all previous releases.