diff --git a/docs/source/usersguide/input.rst b/docs/source/usersguide/input.rst
index e9ce42fd9c..da9896fbb0 100644
--- a/docs/source/usersguide/input.rst
+++ b/docs/source/usersguide/input.rst
@@ -900,7 +900,7 @@ Each ``<surface>`` element can have the following attributes or sub-elements:
      The boundary condition for the surface. This can be "transmission",
      "vacuum", "reflective", or "periodic". Periodic boundary conditions can
      only be applied to x-, y-, and z-planes. Only axis-aligned periodicity is
-     supported, i.e., x-planes an only be paired with x-planes. Specify which
+     supported, i.e., x-planes can only be paired with x-planes. Specify which
      planes are periodic and the code will automatically identify which planes
      are paired together.