diff --git a/README.txt b/README.txt
index dbf5794..56a57fd 100644
--- a/README.txt
+++ b/README.txt
@@ -53,8 +53,9 @@
* Image calculator: apply a mathematical expression to an image or image
channels.
* Discrete Fourier transform: implements the forward and inverse DFT.
- * Percetual hash: detect similar or duplicate images by analyzing and
- comparing their features.
+ * Perceptual hash: maps visually identical images to the same or similar
+ image hash-- useful in image retrieval, authentication, indexing, or
+ copy detection as well as digital watermarking.
* Color management: accurate color management with color profiles or in
lieu of-- built-in gamma compression or expansion as demanded by the
colorspace.