diff --git a/src/averaged_perceptron_tagger.h b/src/averaged_perceptron_tagger.h
index 02a07413..bd9bcfe4 100644
--- a/src/averaged_perceptron_tagger.h
+++ b/src/averaged_perceptron_tagger.h
@@ -3,7 +3,9 @@ averaged_perceptron_tagger.h
 ----------------------------
 
 An averaged perceptron tagger is a greedy sequence labeling
-algorithm which uses two tags of history.
+algorithm which uses features of the current token, surrounding
+tokens and n (typically n=2) previous predictions to predict
+the current value.
 
 */