I m installing office 365 and is asking for OS 10.14.

macOS Mojave 10.14.6 - Technical Specifications

General Requirements

OS X 10.8 or later

2GB of memory

12.5GB of available storage (OS X El Capitan 10.11.5 or later)*

Some features require an Apple ID; terms apply.

Some features require a compatible Internet service provider; fees may apply.

Mac Hardware Requirements

For details about your Mac model, click the Apple icon at the top left of your screen and choose About This Mac. These Mac models are compatible with macOS Mojave:

MacBook (Early 2015 or newer)

MacBook Air (Mid 2012 or newer)

MacBook Pro (Mid 2012 or newer)

Mac mini (Late 2012 or newer)

iMac (Late 2012 or newer)

iMac Pro (2017)

Mac Pro (Late 2013; Mid 2010 and Mid 2012 models with recommended Metal-capable graphics cards)

Don't use FireFox for these links…

https://itunes.apple.com/us/app/macos-mojave/id1398502828?mt=12

ivettemontes Said:

"I m installing office 365 and is asking for OS 10.14.: how do i upgrade to OS 10.14. my imac is mid 2011 and is running on 10.13.: I need 10.14 to install office 365"

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Contact Microsoft:

Contact Microsoft, seeing of they offer a workaround of sorts. Start Here:  Microsoft Contact Us Virtual Agent - Microsoft Support. Perform a chat session with Microsoft using a computer, as it would be more user-friendly doing so.

Microsoft tracks Apple's three-year sliding window of support for the current operating system, and two previous year's major versions. When macOS Monterey is finally released, Microsoft will make macOS Catalina (10.15.7) the minimum operating system to install Microsoft 365/Office 2021 for Mac. You would need a newer Mac that can.support Catalina or later to keep up with Microsoft's minimum installation requirements.

It won't be long before free and fee third-party Office Suite vendors also require Mojave or later. The free LibreOffice Suite and fee SoftMaker Office 2021 each require macOS Sierra (10.12.6) or later.

Macs need to be 2012 or newer to install Mojave. 2011 and older Macs lack the video hardware Mojave requires.