diff --git a/docs/handbook/concepts.rst b/docs/handbook/concepts.rst
index 2dc509a13..842d4248e 100644
--- a/docs/handbook/concepts.rst
+++ b/docs/handbook/concepts.rst
@@ -24,7 +24,7 @@ To get the number and names of bands in an image, use the
 Modes
 -----
 
-The :term:`mode` of an image defines the type and depth of a pixel in the
+The :term:`mode` of an image is a string that defines the type and depth of a pixel in the
 image. The current release supports the following standard modes:
 
     * ``1`` (1-bit pixels, black and white, stored with one pixel per byte)