diff --git a/specification/common/common.md b/specification/common/common.md
index 3e5f1704560..f1198a4d77d 100644
--- a/specification/common/common.md
+++ b/specification/common/common.md
@@ -105,3 +105,14 @@ attribute limits for Resources.
 Attributes, which belong to Metrics, are exempt from the limits described above
 at this time, as discussed in
 [Metrics Attribute Limits](../metrics/sdk.md#attribute-limits).
+
+## Attribute Collections
+
+[Resources](../resource/sdk.md), Metrics
+[data points](../metrics/datamodel.md#metric-points),
+[Spans](../trace/api.md#set-attributes), Span
+[Events](../trace/api.md#add-events), Span
+[Links](../trace/api.md#specifying-links) and
+[Log Records](../logs/data-model.md) may contain a collection of attributes. The
+keys in each such collection are unique, i.e. there cannot exit more than one
+key-value pair with the same key.