kwtm2 1309836018 learn A Posix-compliant *shell* recognizes the set of all Posix features (and possibly a superset, such as in the case of bash). A Posix-compliant *script* is limited to a *subset* of Posix features. A Posix-compliant shell such as bash can handle non-Posix-compliant scripts (such as one that uses bash-only features).
kwtm2 1309926409 forget
kwtm2 1309926415 learn A Posix-compliant *shell* recognizes the set of all Posix features (and possibly also non-Posix features, as in the case of bash). A Posix-compliant *script* is limited to only Posix features. It's possible for a Posix-compliant shell such as bash to handle non-Posix-compliant scripts (e.g. scripts that use bash-only features).