diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -1696,7 +1696,7 @@ def debugdag(ui, repo, file_=None, *revs
     """format the changelog or an index DAG as a concise textual description
 
     If you pass a revlog index, the revlog's DAG is emitted. If you list
-    revision numbers, they get labelled in the output as rN.
+    revision numbers, they get labeled in the output as rN.
 
     Otherwise, the changelog DAG of the current repo is emitted.
     """
diff --git a/mercurial/dagparser.py b/mercurial/dagparser.py
--- a/mercurial/dagparser.py
+++ b/mercurial/dagparser.py
@@ -56,13 +56,13 @@ def parsedag(desc):
         ... :forkhere  # a label for the last of the 3 nodes from above
         ... +5         # 5 more nodes on one branch
         ... :mergethis # label again
-        ... <forkhere  # set default parent to labelled fork node
+        ... <forkhere  # set default parent to labeled fork node
         ... +10        # 10 more nodes on a parallel branch
         ... @stable    # following nodes will be annotated as "stable"
         ... +5         # 5 nodes in stable
         ... !addfile   # custom command; could trigger new file in next node
         ... +2         # two more nodes
-        ... /mergethis # merge last node with labelled node
+        ... /mergethis # merge last node with labeled node
         ... +4         # 4 more nodes descending from merge node
         ...
         ... """)))
diff --git a/mercurial/parser.py b/mercurial/parser.py
--- a/mercurial/parser.py
+++ b/mercurial/parser.py
@@ -13,7 +13,7 @@
 # tokenizer is an iterator that returns type, value pairs
 # elements is a mapping of types to binding strength, prefix and infix actions
 # an action is a tree node name, a tree label, and an optional match
-# __call__(program) parses program into a labelled tree
+# __call__(program) parses program into a labeled tree
 
 import error
 from i18n import _