diff --git a/app/difficulty.py b/app/difficulty.py
index 8ce2577..6d8885c 100644
--- a/app/difficulty.py
+++ b/app/difficulty.py
@@ -7,7 +7,7 @@
 
 import pickle
 import math
-from nltk.stem import WordNetLemmatizer
+from nltk.stem import WordNetLemmatizer # using WordNetLemmatizer for better performance
 from wordfreqCMD import remove_punctuation, freq, sort_in_descending_order, sort_in_ascending_order