DOC: Reword Series.interpolate docstring for clarity

Author: nmusolino

pandas/core/generic.py

@@ -6618,10 +6618,10 @@ def replace(self, to_replace=None, value=None, inplace=False, limit=None,
             * 'pad': Fill in NaNs using existing values.
             * 'nearest', 'zero', 'slinear', 'quadratic', 'cubic', 'spline',
               'barycentric', 'polynomial': Passed to
-              `scipy.interpolate.interp1d`. Both 'polynomial' and 'spline'
-              require that you also specify an `order` (int),
-              e.g. ``df.interpolate(method='polynomial', order=5)``.
-              These use the numerical values of the index.
+              `scipy.interpolate.interp1d`. These methods use the numerical
+              values of the index.  Both 'polynomial' and 'spline' require that
+              you also specify an `order` (int), e.g.
+              ``df.interpolate(method='polynomial', order=5)``.
             * 'krogh', 'piecewise_polynomial', 'spline', 'pchip', 'akima':
               Wrappers around the SciPy interpolation methods of similar
               names. See `Notes`.