use "behavior" instead of "behaviour"

contributing/code_of_conduct/concrete_example_document.rst

@@ -2,7 +2,7 @@ Code of Conduct: Concrete Example Document
 ==========================================
 
 This is a living document that serves to give concrete examples of
-unwanted behaviour. These examples have all taken place somewhere in the
+unwanted behavior. These examples have all taken place somewhere in the
 PHP community in the past, and are clear code of conduct violations
 according to the Symfony code of conduct.
 

contributing/diversity/governance.rst

@@ -121,7 +121,7 @@ management systems should be set up and monitored.
 Openness and Accountability
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The behaviour and conduct of the initiative's guidance team sets the tone for
+The behavior and conduct of the initiative's guidance team sets the tone for
 the rest of the community. The guidance team should lead by example to create a
 culture that enables members to feel it is safe to suggest, question and
 challenge - rather than avoid - difficult ideas and topics. The team should

contributing/documentation/format.rst

@@ -175,7 +175,7 @@ If you are documenting a brand new feature, a change or a deprecation that's
 been made in Symfony, you should precede your description of the change with
 the corresponding directive and a short description:
 
-For a new feature or a behaviour change use the ``.. versionadded:: 3.x``
+For a new feature or a behavior change use the ``.. versionadded:: 3.x``
 directive:
 
 .. code-block:: rst

reference/configuration/framework.rst

@@ -792,7 +792,7 @@ strict_requirements
 
 **type**: ``mixed`` **default**: ``true``
 
-Determines the routing generator behaviour. When generating a route that
+Determines the routing generator behavior. When generating a route that
 has specific :doc:`requirements </routing/requirements>`, the generator
 can behave differently in case the used parameters do not meet these requirements.