> The POSIX Shell is a standardized subset of Bash which has even better portability.
It would be much more correct to say that bash's features are a superset of the shell features standardised by the POSIX standard, as is the case for several other shells (each adding their own parts on top of the standard) too.
It would be much more correct to say that bash's features are a superset of the shell features standardised by the POSIX standard, as is the case for several other shells (each adding their own parts on top of the standard) too.