cherry pick the commit from #34610

src/sage/rings/lazy_series.py

@@ -4344,7 +4344,7 @@ def __call__(self, *g, check=True):
         Given a Taylor series `f` of arity `n` and a tuple of Taylor
         series `g = (g_1,\dots, g_n)` over the same base ring, the
         composition `f \circ g` is defined if and only if for each
-        `1\leq k\leq n`:
+        `1\leq i\leq n`:
 
         - `g_i` is zero, or
         - setting all variables except the `i`-th in `f` to zero
@@ -5285,7 +5285,7 @@ def __call__(self, *args, check=True):
         Given a lazy symmetric function `f` of arity `n` and a tuple
         of lazy symmetric functions `g = (g_1,\dots, g_n)` over the
         same base ring, the composition (or plethysm) `(f \circ g)`
-        is defined if and only if for each `1\leq k\leq n`:
+        is defined if and only if for each `1\leq i\leq n`:
 
         - `g_i = 0`, or
         - setting all alphabets except the `i`-th in `f` to zero