To remove an alias, the unalias command is used. For example, to remove the previously set alias, we use the unalias command as follows:
$ unalias x
The alias command will set its alias for the current session only. If you want to set an alias for any command persistently, you have to make an entry for it in /etc/bashrc for system-wide changes, and if you want to make user-specific changes, than put its entry in the .bashrc file stored in the user's home directory.