Huh? Using a shell interactively is a REPL. REPL means Read-Eval-Print-Loop. That's what you do when you type commands to a bach/zsh/fish/nushell/... prompt. But it also how you type commands to a gnuplot or Mathematica or APL or Python or Lisp prompt.

Some REPLs have nicer interactive features (such a completion than others). Some REPLs have nicer or more powerful syntax or different data types. But as longs as you have a Read-Eval-Print-Loop it's a REPL.