Some of us speak more than one language, and we may at different times prefer one over the other on the Mac. In some cases, we might also have licensed software that only works when the app or macOS is set to a particular language or keyboard.
Apple lets you perform a global or app-specific language change, which is quite handy. (Having a problem with the language selected with macOS Recovery? See this column from last year.)
To change your language for macOS, you start with the Language & Region preference pane. If you don’t see it in System Preferences—it didn’t show up for me in macOS Catalina—choose it from the View menu with System Preferences open.

The Language & Region pane allows you to switch among languages or formats if you rely on multiple ones.
If you’ve already selected keyboard layouts from across multiple languages in the Keyboard preference pane’s Input Methods tab, you see the associated languages listed under Preferred Languages.
You can add additional languages by clicking the + sign at the lower-left corner and then choosing from a list and clicking Add. Some of these entries are more properly dialects than languages, such as the several kinds of English. When you add a language, the pane prompts you to ask if you want that to become your Primary language.
If you decline, you can later drag the language to the top of the Preferred Languages list to make that change. Click the gear icon and choose the menu option to apply your choice here to the login window.
The region setting is separate, but the user interface makes that unclear, as you might think that your preferred language choice would also set the region—and the name region is misleading. Choose a country from the Region pop-up menu, which is indeed divided into regions. That selection will populate the rest of the tab, such as the kind of calendar system used and, and display how dates, quantities, and currency will be displayed.
To set the language for a particular app, click the Apps tab in the pane. You can then choose an app and the associated language.

You can set a language for a particular app, too.
This Mac 911 article is in response to a question submitted by Macworld reader Verna.
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