Fundamentals and usage
================

This section introduces the fundamentals you need before running synthesis or fitting in PySME.
It covers the key data structures and controls that define spectra, line selection, and model behavior.

.. toctree::
   :maxdepth: 1

   mask.md
   rv.md
   continuum.md
   linelist.md
   abund.md
   segment.md
   flux_inten.md
   io.md