diff --git a/doc/design/cluster_train/trainer.md b/doc/design/cluster_train/trainer.md
index 638cfb179b802d06afa6862168669c7edeaf9431..c9c090dc984866bcc769fc45c902865610d7e545 100644
--- a/doc/design/cluster_train/trainer.md
+++ b/doc/design/cluster_train/trainer.md
@@ -27,7 +27,7 @@ const (
 	Float64
 )
 
-// Parameter is a piece data to sync with the parameter server.
+// Parameter is a piece of data to sync with the parameter server.
 type Parameter struct {
 	Name        string
 	ElementType ElementType