I was inspired by the question Mac or Macintosh.

What's the proper way to pronounce "Mac OS X"? I've heard the following things used to refer to the operating system on the Macintosh:

  • "Mac OS Ten" ("OS" is said like "AHSS")
  • "Mac OS Ex" ("OS" is said like "AHSS")
  • "Mac Oh-Ess Ex"
  • "Mac Oh-Ess Ten"
  • "Darwin" (People use this to refer to the operating system. Is this correct?)
  • 2
    I say "OSX" Oh-Es-Ex most of the time.
    – Josh K
    Commented Sep 23, 2010 at 20:58
  • 2
    Forgive my non-native ignorance, but what's the difference between "OS Ex" and "Oh-Ess Ex"? Do you pronounce "OS Ex" like "Ossex"? :)
    – deceze
    Commented Sep 24, 2010 at 3:15
  • 1
    @deceze: I was following the OP's lead with that, I say "O" then "S" then "X".
    – Josh K
    Commented Sep 24, 2010 at 15:57
  • @deceze : I'll update my post to see if I can make it more clear. It's hard to pronounce things in ascii. "In cyberspace, nobody can hear you scream." Commented Sep 24, 2010 at 17:30
  • Wow, seriously, "Mac Ohs Ex"? It would never have occurred to me to pronounce it that way. :)
    – deceze
    Commented Sep 24, 2010 at 23:14

10 Answers 10


According to Apple

The current version of Mac OS is Mac OS X (pronounced "Mac O-S ten"). ... . Major releases of Mac OS X include versions 10.0, 10.3, and 10.4. There are also updates (sometimes called "dot" releases) for each major release, such as versions 10.2.8 and 10.4.2.

This does present a problem because it isn't correct to write Mac OS X.6. All references to Mac OS X 10.6, are easier to pronounce as "Oh Ess [Ex] ten dot/point six," rather than saying, "ten," twice.

As for Darwin,

The Darwin layer of Mac OS X comprises the kernel, drivers, and BSD portions of the system [...]. Mac OS X extends this low-level environment with several core infrastructure technologies that make it easier for you to develop software.

Apple purchased NeXT for their XNU kernel, which is a hybrid kernel forked from CMU's Mach microkernel. BSD is an implementation of Unix originally released through UC Berkley. Aqua is the rendering engine for the user interface. The Apple Finder is a system application that always runs for user access to files and the desktop. OS X is the sum of these and other parts.

  • The Darwin kernel was based on the Mach Microkernel from CMU. The BSD kernel was monolithic, like the Linux kernel is. The Unix system living on top of the kernel was derived from BSD. Apple people always seem to get this wrong for some reason. Commented Sep 26, 2010 at 0:39
  • @Adam, Thanks, I'll fix that. I recognized that the kernel wasn't Unix by itself, and I knew there was something special about the micro-kernel, but hadn't looked into it lately.
    – SpecKK
    Commented Sep 27, 2010 at 17:40
  • no prob. I've seen a lot of references to OSX having a "BSD kernel" lately and it's been getting on my nerves :) Commented Sep 27, 2010 at 19:41
  • 1
    +1 for illustrating why saying it like Mac O S Ten causes a problem. However, I think Apple would probably respond by saying that you should really be saying "Mac OS Ten Snow Leopard", or just Snow Leopard rather than "Mac OS Ten 10.6" :) Commented Jun 5, 2011 at 19:50

Try typing

say Mac OS X

in Terminal. You'll hear what Apple thinks about it.

Hint: It's "mac oh es ten"

  • 7
    Mac Oh-Ess Ten…
    – ghoppe
    Commented Sep 23, 2010 at 20:23
  • hehe, right ... but that isn't an option in OP's list :-) (I've updated the answer though) Commented Sep 23, 2010 at 20:29
  • +++++ can't believe I didn't know about say before... I've been having far too much fun with it now that I saw this post :) Commented Sep 24, 2010 at 0:33
  • 3
    @Stefan In a word, yes. This is precisely the sort of detail Apple sweats over. The Wrath of Steve would be swift and merciless had they got it "wrong". It had to have been changed, since "X" would never be pronounced "ten" in any other context.
    – ghoppe
    Commented Sep 24, 2010 at 17:38
  • 1
    Steve would have said the v doesn't belong there. Take the v out, and say Mac OS X 10.6 Snow Leopard and you get the right answer.
    – Daniel
    Commented Feb 29, 2012 at 16:36

starting with mountain lion it's no longer "mac os x" it will be just "OS X" pronounced o s ten.

  • They have also revised Lion's webpages to now show "OS X Lion" e.i. removed Mac.
    – pdd
    Commented Feb 29, 2012 at 19:03

From: http://support.apple.com/kb/TA22541

The current version of Mac OS is Mac OS X (pronounced "Mac O-S ten")


Mac Oh-Ess Ten

"Darwin" (People use this to refer to the operating system. Is this correct?)

Only partially. Darwin is the open-source unix-derived foundation of the operating system upon which GUI-goodness, frameworks, application environments, core services and other proprietary bells and whistles are laid.


They call it Macaussexx on the Dev Show (it's a joke though).


I know what it's supposed to be, but every time I speak it, it comes out of my mouth like "Mac Oh-Ess Ecks".

  • I'm the same way. I see a letter amongst others and therefore I pronounce it as "X" not ten.
    – Kyle Hayes
    Commented Aug 19, 2011 at 17:47
  • You are not alone - many people prefer X and persist even when faced with what some people feel is the "canonical" answer.
    – bmike
    Commented Feb 29, 2012 at 15:32

Apple uses different names for different versions of the Mac operating system, as well as gradually migrating from version number to preferring version names. The Apple Style Guide shows how to write them, but not how to pronounce them. Combining that with various other sources, I get:

  • 10.0 through 10.7: Write "Mac OS X", and pronounce it "Mac O-S ten" (source, from SpecKK's answer). Include the version number only, as in "Mac OS X 10.7" (presumably pronounced "Mac O-S ten ten point seven").
  • 10.8 through 10.11: Write "OS X", and pronounce it "O-S ten" (source: Craig Federighi). Use the code name, version number, or both, as in "OS X El Capitan 10.11" (pronounced "O-S ten El Capitan ten point eleven").
  • 10.12 or later (at least through 11.2): Write "macOS", and pronounce it "mac O-S" (source: Craig again). Again, use the code name, version number, or both, as in "macOS Sierra 10.12" (pronounced "mac O-S Sierra ten point twelve").

Part of me asks "How is this even a real question or up for debate*?", but of course the confusion was set in prior versions of Mac OS 8 and 9 have one obvious pronunciation.

The way that Apple Employees pronounce (and nearly all Mac fans agree) is that the X represents 10 exclusively and should not be spoken or expanded into the letter "X"

Mac Oh Es Ten

* That were actually labelled as Mac OS 8 & 9 and not as Mac OS IX & Mac OS XIII. Perhaps that is one reason there is a debate. Also, the infrequent use of Roman numbers in applications apart from clock faces. Perhaps the Mac OS X brand was in reference to the X "hipness" of Next and Unix as Apple replaced their previous OS architecture with one based on Next/Unix heritage.

  • 1
    And System 7 before that.
    – Ɱark Ƭ
    Commented Jan 28, 2011 at 15:47
  • Absolutely the "X" is a reference to NeXT influence on OS X.
    – Dan Ray
    Commented Feb 29, 2012 at 18:39

When I was a kid developer, we were still using latin numerals so it wasn't hard to see OS 9 moving aside for OS X pronounced "Ten" but with a latin numeral "X" to honor the new Unix core.

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