diff --git a/index.bs b/index.bs
index 16de558..84d0a37 100644
--- a/index.bs
+++ b/index.bs
@@ -525,7 +525,7 @@ At an <a>implementation-defined</a> interval <var>interval</var>, the user agent
     1. If <var>rotationRate</var>'s <a for="DeviceMotionEventRotationRate">x axis rotation rate</a> is not null, limit its precision to no more than 0.1 deg/s.
     1. Set <var>rotationRate</var>'s <a for="DeviceMotionEventRotationRate">y axis rotation rate</a> to the device's <a>rotation rate</a> about the Y axis, or null if it cannot be provided.
     1. If <var>rotationRate</var>'s <a for="DeviceMotionEventRotationRate">y axis rotation rate</a> is not null, limit its precision to no more than 0.1 deg/s.
-    1. Set <var>rotationRate</var>'s <a for="DeviceMotionEventRotationRate">z axis rotation rate</a> to the device's <a>rotation rate</a> along the Z axis, or null if it cannot be provided.
+    1. Set <var>rotationRate</var>'s <a for="DeviceMotionEventRotationRate">z axis rotation rate</a> to the device's <a>rotation rate</a> about the Z axis, or null if it cannot be provided.
     1. If <var>rotationRate</var>'s <a for="DeviceMotionEventRotationRate">z axis rotation rate</a> is not null, limit its precision to no more than 0.1 deg/s.
   1. <a>Fire an event</a> named <a event for="Window"><code>devicemotion</code></a> at <var>window</var>, using {{DeviceMotionEvent}}, with the {{DeviceMotionEvent/acceleration}} attribute initialized to <var>acceleration</var>, the {{DeviceMotionEvent/accelerationIncludingGravity}} attribute initialized to <var>accelerationIncludingGravity</var>, the {{DeviceMotionEvent/rotationRate}} attribute initialized to <var>rotationRate</var>, and the {{DeviceMotionEvent/interval}} attribute initialized to <var>interval</var>.