Small fix

chapter18.tex

@@ -689,9 +689,9 @@ using a depth-first search:
 \end{tikzpicture}
 \end{center}
 
-
-However, we use a bit different technique where
-we add each node to the tree traversal array \emph{always}
+However, we use a bit different variant of
+the tree traversal array where
+we add each node to the array \emph{always}
 when the depth-first search visits the node,
 and not only at the first visit.
 Hence, a node that has $k$ children appears $k+1$ times