diff --git a/analyse/idf.go b/analyse/idf.go
index c054f5e..37e50eb 100644
--- a/analyse/idf.go
+++ b/analyse/idf.go
@@ -38,7 +38,7 @@ func (i *Idf) loadDictionary(fileName string) error {
 	return dictionary.LoadDictionary(i, fileName)
 }
 
-func (i Idf) Frequency(key string) (float64, bool) {
+func (i *Idf) Frequency(key string) (float64, bool) {
 	i.RLock()
 	freq, ok := i.freqMap[key]
 	i.RUnlock()
diff --git a/analyse/stopwords.go b/analyse/stopwords.go
index ac2f598..81012f7 100644
--- a/analyse/stopwords.go
+++ b/analyse/stopwords.go
@@ -57,7 +57,7 @@ func NewStopWord() *StopWord {
 	return s
 }
 
-func (s StopWord) IsStopWord(word string) bool {
+func (s *StopWord) IsStopWord(word string) bool {
 	s.RLock()
 	_, ok := s.stopWordMap[word]
 	s.RUnlock()
diff --git a/dictionary.go b/dictionary.go
index 2cc8bb6..d8805b8 100644
--- a/dictionary.go
+++ b/dictionary.go
@@ -7,12 +7,14 @@ import (
 	"github.com/wangbin/jiebago/dictionary"
 )
 
+// A Dictionary represents a thread-safe dictionary used for word segmentation.
 type Dictionary struct {
 	total, logTotal float64
 	freqMap         map[string]float64
 	sync.RWMutex
 }
 
+// Load loads all tokens from channel
 func (d *Dictionary) Load(ch <-chan dictionary.Token) {
 	d.Lock()
 	for token := range ch {
@@ -22,6 +24,7 @@ func (d *Dictionary) Load(ch <-chan dictionary.Token) {
 	d.updateLogTotal()
 }
 
+// AddToken adds one token
 func (d *Dictionary) AddToken(token dictionary.Token) {
 	d.Lock()
 	d.addToken(token)
@@ -46,7 +49,8 @@ func (d *Dictionary) updateLogTotal() {
 	d.logTotal = math.Log(d.total)
 }
 
-func (d Dictionary) Frequency(key string) (float64, bool) {
+// Frequency returns the frequency of give word, if not found, the second result is false
+func (d *Dictionary) Frequency(key string) (float64, bool) {
 	d.RLock()
 	freq, ok := d.freqMap[key]
 	d.RUnlock()
diff --git a/posseg/dictionary.go b/posseg/dictionary.go
index 2618464..e4fee3b 100644
--- a/posseg/dictionary.go
+++ b/posseg/dictionary.go
@@ -50,14 +50,14 @@ func (d *Dictionary) updateLogTotal() {
 	d.logTotal = math.Log(d.total)
 }
 
-func (d Dictionary) Frequency(key string) (float64, bool) {
+func (d *Dictionary) Frequency(key string) (float64, bool) {
 	d.RLock()
 	freq, ok := d.freqMap[key]
 	d.RUnlock()
 	return freq, ok
 }
 
-func (d Dictionary) Pos(key string) (string, bool) {
+func (d *Dictionary) Pos(key string) (string, bool) {
 	d.RLock()
 	pos, ok := d.posMap[key]
 	d.RUnlock()