diff --git a/src/Orchard/IDependency.cs b/src/Orchard/IDependency.cs
index 887ff8a70..82262c5af 100644
--- a/src/Orchard/IDependency.cs
+++ b/src/Orchard/IDependency.cs
@@ -2,12 +2,21 @@
 using Orchard.Logging;
 
 namespace Orchard {
+    /// <summary>
+    /// Base interface for services that are instantiated per unit of work (i.e. web request).
+    /// </summary>
     public interface IDependency {
     }
 
+    /// <summary>
+    /// Base interface for services that are instantiated per shell/tenant.
+    /// </summary>
     public interface ISingletonDependency : IDependency {
     }
 
+    /// <summary>
+    /// Base interface for services that are instantiated per usage.
+    /// </summary>
     public interface ITransientDependency : IDependency {
     }