diff --git a/source/reference/glossary.txt b/source/reference/glossary.txt
index b0ca98ef40e..92e94b0f2be 100644
--- a/source/reference/glossary.txt
+++ b/source/reference/glossary.txt
@@ -442,7 +442,7 @@ Glossary
    natural order
       The order in which a database stores documents on
       disk. Typically, the order of documents on disks reflects
-      insertion order, *except* when documents move internal because
+      insertion order, *except* when documents move internally because
       of document growth due to update operations. However,
       :term:`Capped collections <capped collection>` guarantee that
       insertion order and natural order are identical.
@@ -810,9 +810,10 @@ Glossary
       ages it out.
 
    ObjectId
-      A special 12-byte :term:`BSON` type that has a high probability
-      an ObjectId represent the time of the ObjectId's
-      creation. MongoDB uses ObjectId values as the default values for
+      A special 12-byte :term:`BSON` type that guarantees uniqueness
+      within the collection. The ObjectID is generated based on
+      timestamp, machine ID, process ID, and a process-local incremental
+      counter. MongoDB uses ObjectId values as the default values for
       :term:`_id` fields.
 
    geohash