diff --git a/source/module_md/md_base.h b/source/module_md/md_base.h
index af25505c26..1d63155821 100644
--- a/source/module_md/md_base.h
+++ b/source/module_md/md_base.h
@@ -8,7 +8,7 @@
  * @brief base class of md
  *
  * This class implements the velocity-Verlet method.
- * The system is assumed to be isolated in the sense that it cannot exchange energy or particles with its environment,
+ * The corresponding system(nve) is assumed to be isolated in the sense that it cannot exchange energy or particles with its environment,
  * so that the energy of the system does not change with time.
  */
 class MD_base
@@ -88,4 +88,4 @@ class MD_base
     double energy_;  ///< total energy of the system
 };
 
-#endif // MD_BASE_H
\ No newline at end of file
+#endif // MD_BASE_H