Linux is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel.

Solution
Change the language.
Instructions on how to change the language.
- Show Applications
- Click on Settings
- Click on Region & Language
- Change Language (e.g. current language: English (United States), new language: English (United Kingdom)
- Click on the Select button
- Click on the restart Restart button
- Log out
- Log in
Now you can change the previous language back, e.g. English (United States).
Open terminal (Ctrl + Alt + T).
The terminal should work.