Question: what is os x 10.9.5?
Answer: OS X Mavericks (version 10.9) is the tenth major release of OS X (since June 2016 rebranded as macOS), Apple Inc.'s desktop and server operating system for Macintosh computers. OS X Mavericks was announced on June 10, 2013, at WWDC 2013, and was released on October 22, 2013 worldwide.