diff --git a/contrib/vim/patchreview.txt b/contrib/vim/patchreview.txt
--- a/contrib/vim/patchreview.txt
+++ b/contrib/vim/patchreview.txt
@@ -30,7 +30,7 @@ but can not handle patch files containin
 software development projects. This plugin provides that missing
 functionality.
 
-It also improves on |:diffpatch|'s behaviour of creating the patched files in
+It also improves on |:diffpatch|'s behavior of creating the patched files in
 the same directory as original file which can lead to project workspace
 pollution.
 
diff --git a/hgext/eol.py b/hgext/eol.py
--- a/hgext/eol.py
+++ b/hgext/eol.py
@@ -23,7 +23,7 @@ declared to be binary (``BIN``) are left
 ``native`` is an alias for checking out in the platform's default line
 ending: ``LF`` on Unix (including Mac OS X) and ``CRLF`` on
 Windows. Note that ``BIN`` (do nothing to line endings) is Mercurial's
-default behaviour; it is only needed if you need to override a later,
+default behavior; it is only needed if you need to override a later,
 more general pattern.
 
 The optional ``[repository]`` section specifies the line endings to
diff --git a/hgext/histedit.py b/hgext/histedit.py
--- a/hgext/histedit.py
+++ b/hgext/histedit.py
@@ -144,7 +144,7 @@ repository that Mercurial does not detec
 repo, you can add a ``--force`` option.
 
 Histedit rule lines are truncated to 80 characters by default. You
-can customise this behaviour by setting a different length in your
+can customise this behavior by setting a different length in your
 configuration file::
 
   [histedit]
diff --git a/hgext/mq.py b/hgext/mq.py
--- a/hgext/mq.py
+++ b/hgext/mq.py
@@ -28,7 +28,7 @@ Common tasks (use :hg:`help command` for
 
 By default, mq will automatically use git patches when required to
 avoid losing file mode changes, copy records, binary files or empty
-files creations or deletions. This behaviour can be configured with::
+files creations or deletions. This behavior can be configured with::
 
   [mq]
   git = auto/keep/yes/no
diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -1436,10 +1436,10 @@ class changeset_templater(changeset_prin
 
         showlist = templatekw.showlist
 
-        # showparents() behaviour depends on ui trace level which
-        # causes unexpected behaviours at templating level and makes
+        # showparents() behavior depends on ui trace level which
+        # causes unexpected behaviors at templating level and makes
         # it harder to extract it in a standalone function. Its
-        # behaviour cannot be changed so leave it here for now.
+        # behavior cannot be changed so leave it here for now.
         def showparents(**args):
             ctx = args['ctx']
             parents = [[('rev', p.rev()),
@@ -1929,7 +1929,7 @@ def _makelogrevset(repo, pats, opts, rev
         followfirst = 1
     else:
         followfirst = 0
-    # --follow with FILE behaviour depends on revs...
+    # --follow with FILE behavior depends on revs...
     it = iter(revs)
     startrev = it.next()
     followdescendants = startrev < next(it, startrev)
@@ -2050,7 +2050,7 @@ def _makelogrevset(repo, pats, opts, rev
     return expr, filematcher
 
 def _logrevs(repo, opts):
-    # Default --rev value depends on --follow but --follow behaviour
+    # Default --rev value depends on --follow but --follow behavior
     # depends on revisions resolved from --rev...
     follow = opts.get('follow') or opts.get('follow_first')
     if opts.get('rev'):
diff --git a/mercurial/mail.py b/mercurial/mail.py
--- a/mercurial/mail.py
+++ b/mercurial/mail.py
@@ -31,10 +31,10 @@ def _unifiedheaderinit(self, *args, **kw
     constructor, and 2.7 removed this parameter.
 
     Default argument is continuation_ws=' ', which means that the
-    behaviour is different in <2.7 and 2.7
+    behavior is different in <2.7 and 2.7
 
-    We consider the 2.7 behaviour to be preferable, but need
-    to have an unified behaviour for versions 2.4 to 2.7
+    We consider the 2.7 behavior to be preferable, but need
+    to have an unified behavior for versions 2.4 to 2.7
     """
     # override continuation_ws
     kw['continuation_ws'] = ' '
diff --git a/mercurial/parsers.c b/mercurial/parsers.c
--- a/mercurial/parsers.c
+++ b/mercurial/parsers.c
@@ -682,7 +682,7 @@ typedef struct {
 } nodetree;
 
 /*
- * This class has two behaviours.
+ * This class has two behaviors.
  *
  * When used in a list-like way (with integer keys), we decode an
  * entry in a RevlogNG index file on demand. Our last entry is a
diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -1062,7 +1062,7 @@ class filecache(object):
     Mercurial either atomic renames or appends for files under .hg,
     so to ensure the cache is reliable we need the filesystem to be able
     to tell us if a file has been replaced. If it can't, we fallback to
-    recreating the object on every call (essentially the same behaviour as
+    recreating the object on every call (essentially the same behavior as
     propertycache).
 
     '''
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -2260,7 +2260,7 @@ def sizetoint(s):
 
 class hooks(object):
     '''A collection of hook functions that can be used to extend a
-    function's behaviour. Hooks are called in lexicographic order,
+    function's behavior. Hooks are called in lexicographic order,
     based on the names of their sources.'''
 
     def __init__(self):
diff --git a/tests/test-filecache.py b/tests/test-filecache.py
--- a/tests/test-filecache.py
+++ b/tests/test-filecache.py
@@ -130,7 +130,7 @@ def fakeuncacheable():
     util.cachestat.__init__ = originit
 
 def test_filecache_synced():
-    # test old behaviour that caused filecached properties to go out of sync
+    # test old behavior that caused filecached properties to go out of sync
     os.system('hg init && echo a >> a && hg ci -qAm.')
     repo = hg.repository(ui.ui())
     # first rollback clears the filecache, but changelog to stays in __dict__
diff --git a/tests/test-filelog.py b/tests/test-filelog.py
--- a/tests/test-filelog.py
+++ b/tests/test-filelog.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 """
-Tests the behaviour of filelog w.r.t. data starting with '\1\n'
+Tests the behavior of filelog w.r.t. data starting with '\1\n'
 """
 from mercurial import ui, hg
 from mercurial.node import nullid, hex
diff --git a/tests/test-mq.t b/tests/test-mq.t
--- a/tests/test-mq.t
+++ b/tests/test-mq.t
@@ -39,7 +39,7 @@ help
   
   By default, mq will automatically use git patches when required to avoid
   losing file mode changes, copy records, binary files or empty files creations
-  or deletions. This behaviour can be configured with:
+  or deletions. This behavior can be configured with:
   
     [mq]
     git = auto/keep/yes/no
diff --git a/tests/test-pathencode.py b/tests/test-pathencode.py
--- a/tests/test-pathencode.py
+++ b/tests/test-pathencode.py
@@ -2,7 +2,7 @@
 # time it is invoked, and tests the encoding of those pathnames.
 #
 # It uses a simple probabilistic model to generate valid pathnames
-# that have proven likely to expose bugs and divergent behaviour in
+# that have proven likely to expose bugs and divergent behavior in
 # different encoding implementations.
 
 from mercurial import store