diff --git a/section_synonym.go b/section_synonym.go
index ef237bc..cf52bc6 100644
--- a/section_synonym.go
+++ b/section_synonym.go
@@ -719,7 +719,7 @@ func mergeSynonyms(synItr *SynonymsIterator, newDocNums []uint64, newRoaring *ro
 	synTermMap map[uint32]string, termSynMap map[string]uint32, newSynonymID uint32) (uint32, error) {
 	next, err := synItr.Next()
 	for next != nil && err == nil {
-		synNewDocNum := newDocNums[next.DocNum()]
+		synNewDocNum := newDocNums[next.Number()]
 		if synNewDocNum == docDropped {
 			return 0, fmt.Errorf("see hit with dropped docNum")
 		}
diff --git a/synonym_posting.go b/synonym_posting.go
index c965c16..9bec776 100644
--- a/synonym_posting.go
+++ b/synonym_posting.go
@@ -35,7 +35,7 @@ func init() {
 	var si SynonymsIterator
 	reflectStaticSizeSynonymsIterator = int(reflect.TypeOf(si).Size())
 	var s Synonym
-	reflectStaticSizePosting = int(reflect.TypeOf(s).Size())
+	reflectStaticSizeSynonym = int(reflect.TypeOf(s).Size())
 }
 
 type SynonymsList struct {
@@ -205,7 +205,7 @@ type Synonym struct {
 }
 
 func (p *Synonym) Size() int {
-	sizeInBytes := reflectStaticSizePosting + SizeOfPtr +
+	sizeInBytes := reflectStaticSizeSynonym + SizeOfPtr +
 		len(p.term)
 
 	return sizeInBytes
@@ -215,11 +215,7 @@ func (s *Synonym) Term() string {
 	return s.term
 }
 
-func (s *Synonym) SynonymID() uint32 {
-	return s.synID
-}
-
-func (s *Synonym) DocNum() uint32 {
+func (s *Synonym) Number() uint32 {
 	return s.docNum
 }
 
diff --git a/thesaurus.go b/thesaurus.go
index 28515f9..e488ae6 100644
--- a/thesaurus.go
+++ b/thesaurus.go
@@ -19,6 +19,7 @@ import (
 	"fmt"
 
 	"github.com/RoaringBitmap/roaring"
+	index "github.com/blevesearch/bleve_index_api"
 	segment "github.com/blevesearch/scorch_segment_api/v2"
 	"github.com/blevesearch/vellum"
 )
@@ -112,3 +113,47 @@ func (t *Thesaurus) Contains(key []byte) (bool, error) {
 	}
 	return false, nil
 }
+
+// AutomatonIterator returns an iterator which only visits terms
+// having the the vellum automaton and start/end key range
+func (t *Thesaurus) AutomatonIterator(a segment.Automaton,
+	startKeyInclusive, endKeyExclusive []byte) segment.ThesaurusIterator {
+	if t.fst != nil {
+		rv := &ThesaurusIterator{
+			t: t,
+		}
+
+		itr, err := t.fst.Search(a, startKeyInclusive, endKeyExclusive)
+		if err == nil {
+			rv.itr = itr
+		} else if err != vellum.ErrIteratorDone {
+			rv.err = err
+		}
+
+		return rv
+	}
+	return emptyThesaurusIterator
+}
+
+var emptyThesaurusIterator = &ThesaurusIterator{}
+
+// ThesaurusIterator is an iterator for term dictionary
+type ThesaurusIterator struct {
+	t     *Thesaurus
+	itr   vellum.Iterator
+	err   error
+	entry index.ThesaurusEntry
+}
+
+// Next returns the next entry in the dictionary
+func (i *ThesaurusIterator) Next() (*index.ThesaurusEntry, error) {
+	if i.err != nil && i.err != vellum.ErrIteratorDone {
+		return nil, i.err
+	} else if i.itr == nil || i.err == vellum.ErrIteratorDone {
+		return nil, nil
+	}
+	term, _ := i.itr.Current()
+	i.entry.Term = string(term)
+	i.err = i.itr.Next()
+	return &i.entry, nil
+}