diff --git a/MagickCore/option.c b/MagickCore/option.c
index c5a5b4f..f0bcac1 100644
--- a/MagickCore/option.c
+++ b/MagickCore/option.c
@@ -1597,7 +1597,8 @@
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
-% DefineImageOption() associates a key/value pair with an image option.
+% DefineImageOption() associates an assignment string of the form
+% "key=value" with an image option.
%
% The format of the DefineImageOption method is:
%
@@ -1608,7 +1609,7 @@
%
% o image_info: the image info.
%
-% o option: the image option.
+% o option: the image option assignment string.
%
*/
MagickExport MagickBooleanType DefineImageOption(ImageInfo *image_info,