--- a/docs/concepts.rst	Sat Apr 27 21:09:47 2019 -0400
+++ b/docs/concepts.rst	Sat Apr 27 21:24:18 2019 -0400
@@ -92,8 +92,8 @@
 think of the traditional parent/child DAG as the first derivative of
 your source code, and the obsolescence DAG as the second derivative.)
 
-Troubled changesets (unstable, bumped, divergent)
--------------------------------------------------
+Troubled changesets (orphan, bumped, divergent)
+-----------------------------------------------
 
 Evolving history can introduce problems that need to be solved. For
 example, if you prune a changeset *P* but not its descendants, those
@@ -102,7 +102,7 @@
 at the same time. But Mercurial does not push obsolete changesets like
 *P*, so it cannot push the descendants of *P*. Any non-obsolete
 changeset that is a descendant of an obsolete changeset is said to be
-*unstable*.
+an *orphan*.
 
   [diagram: obsolete cset with non-obsolete descendant]
 
@@ -132,13 +132,13 @@
 successors are both called *divergent* (unless one of them is in
 public phase; only mutable changesets are divergent).
 
-The collective term for unstable, bumped, and divergent changeset is
+The collective term for orphan, bumped, and divergent changeset is
 *troubled*::
 
-  troubled = unstable ∪ bumped ∪ divergent
+  troubled = orphan ∪ bumped ∪ divergent
 
 It is possible for a changeset to be in any of the troubled categories
-at the same time: it might be unstable and divergent, or bumped and
+at the same time: it might be an orphan and divergent, or bumped and
 divergent, or whatever.
 
   [diagram: Venn diagram of troubled changesets, showing overlap]