Microsoft Lumia (previously the Nokia Lumia Series) is a range of mobile devices designed and marketed by Microsoft Mobile and previously by Nokia. Introduced in November 2011, the line was the result of a long-term partnership between Nokia and Microsoft—as such, all Lumia smartphones run the Windows Phone operating system. The Lumia name is derived from the partitive plural form of the Finnish word lumi, meaning "snow". On 3 September 2013, Microsoft announced its purchase of Nokia's mobile device business, with the deal closing on 25 April 2014. As a result, the Lumia line is now maintained by Microsoft Mobile. As part of the transition, Microsoft continued to use the Nokia brand on Lumia devices until October 2014, when it began to officially phase out the Nokia name in its promotion and production of smartphones in favor of Microsoft branding. In November 2014, Microsoft announced the first Microsoft (non-Nokia) branded Lumia device, the Lumia 535. In October 2015, Microsoft announced the first Lumia devices running on Windows 10 Mobile, the Lumia 950, Lumia 950 XL and Lumia 550. The most recent Lumia smartphone, the Lumia 650, was announced by Microsoft on February 15, 2016.