diff --git a/python/swiftest/swiftest/simulation_class.py b/python/swiftest/swiftest/simulation_class.py
index 465ef9c30..846aba347 100644
--- a/python/swiftest/swiftest/simulation_class.py
+++ b/python/swiftest/swiftest/simulation_class.py
@@ -9,7 +9,7 @@
 
 class Simulation:
     """
-    This is a class that define the basic Swift/Swifter/Swiftest simulation object
+    This is a class that defines the basic Swift/Swifter/Swiftest simulation object
     """
     def __init__(self, codename="Swiftest", param_file="", readbin=True):
         self.ds = xr.Dataset()