diff --git a/common/types.go b/common/types.go
index 5ae3418..808f807 100644
--- a/common/types.go
+++ b/common/types.go
@@ -1,3 +1,4 @@
 package common
 
+// SegmentID is a unique identifier for a segment of data @ the shard level.
 type SegmentID string