diff --git a/fastNLP/core/vocabulary.py b/fastNLP/core/vocabulary.py
index 2f2358a1..55a1e3f8 100644
--- a/fastNLP/core/vocabulary.py
+++ b/fastNLP/core/vocabulary.py
@@ -3,13 +3,8 @@ from collections import Counter
 
 DEFAULT_PADDING_LABEL = '<pad>'  # dict index = 0
 DEFAULT_UNKNOWN_LABEL = '<unk>'  # dict index = 1
-DEFAULT_RESERVED_LABEL = ['<reserved-2>',
-                          '<reserved-3>',
-                          '<reserved-4>']  # dict index = 2~4
 
-DEFAULT_WORD_TO_INDEX = {DEFAULT_PADDING_LABEL: 0, DEFAULT_UNKNOWN_LABEL: 1,
-                         DEFAULT_RESERVED_LABEL[0]: 2, DEFAULT_RESERVED_LABEL[1]: 3,
-                         DEFAULT_RESERVED_LABEL[2]: 4}
+DEFAULT_WORD_TO_INDEX = {DEFAULT_PADDING_LABEL: 0, DEFAULT_UNKNOWN_LABEL: 1}
 
 
 def isiterable(p_object):
@@ -58,24 +53,23 @@ class Vocabulary(object):
         self.word2idx = None
         self.idx2word = None
 
-    def update(self, word):
+    def update(self, word_lst):
         """add word or list of words into Vocabulary
 
         :param word: a list of string or a single string
         """
-        if not isinstance(word, str) and isiterable(word):
-            # it's a nested list
-            for w in word:
-                self.update(w)
-        else:
-        # it's a word to be added
-            self.word_count[word] += 1
-            self.word2idx = None
-        return self
+        self.word_count.update(word_lst)
+
+
+    def add(self, word):
+        self.word_count[word] += 1
+
+    def add_word(self, word):
+        self.add(word)
+
+    def add_word_lst(self, word_lst):
+        self.update(word_lst)
 
-    def update_list(self, sent):
-        self.word_count.update(sent)
-        self.word2idx = None
 
     def build_vocab(self):
         """build 'word to index' dict, and filter the word using `max_size` and `min_freq`