MacBook Pro 2015 install app on external drive including a cloud storage drive I would like to install MS Office 2016 on my MacBook Pro but there's not enough space. I thought of installing it on an external USB drive. However, I got an error message that "Microsoft Office 2016 can't be installed on this disk. OS X isn't installed.", and hence I couldn't install it.
Is there anyhow to overcome this situation?
I have one more question which is, is it possible to consider a cloud storage drive like Google Drive as a kind of USB and install an app on it?
Install the application to Macintosh HD (your internal drive). Then go to your Applications folder, move the applications (after they've been installed) to the external drive. Test to make sure the apps on the drive open properly. Then delete the ones in the Applications folder.

Addition: if you have a cloud storage service, you cannot install the apps onto it, but you can store some of your other documents there while you install MS Office on your internal drive.