macOS

Apple's desktop operating system

Pronunciation

Correct

mac-O-S

/mæk oʊ ɛs/

As used in Apple keynotes and official documentation. 'mac' + 'O-S'.

Source: www.apple.com(official spec)

Common Mistake

MAY-koss

/ˈmeɪkɒs/

Reading it as a single word. The 'OS' stands for Operating System and is pronounced separately.