diff --git a/skimage/morphology/selem.py b/skimage/morphology/selem.py
index 8d907d88..d403a27a 100644
--- a/skimage/morphology/selem.py
+++ b/skimage/morphology/selem.py
@@ -212,7 +212,7 @@ def ball(radius, dtype=np.uint8):
 
 def octagon(m, n, dtype=np.uint8):
     """
-    Generates a octagon shaped structuring element with a given size of
+    Generates an octagon shaped structuring element with a given size of
     horizontal and vertical sides and a given height of slanted sides.
     The slanted sides are 45 or 135 degrees to the horizontal axis.