added primary shard glossary entry

source/administration/sharding.txt

@@ -161,7 +161,7 @@ more detail or use the following procedure as a quick starting point:
       MongoDB creates databases automatically upon their first use.
 
       Once you enable sharding for a database, MongoDB assigns a
-      "primary" shard for that database, where MongoDB stores all data
+      :term:`primary shard` for that database, where MongoDB stores all data
       before sharding begins.
 
 #. Enable sharding on a per-collection basis.
@@ -295,7 +295,7 @@ To remove a :term:`shard` from a :term:`shard cluster`, you must:
 
 - Migrate :term:`chunks <chunk>` to another shard or database.
 
-- Ensure that this shard is not the "primary" shard for any databases in
+- Ensure that this shard is not the :term:`primary shard` for any databases in
   the cluster. If it is, move the "primary" status for these databases
   to other shards.
 
@@ -367,7 +367,7 @@ The procedure to remove a shard is as follows:
 #. Move any databases to other shards in the cluster as needed.
 
    This is only necessary when removing a shard that is also the
-   "primary" shard for one or more databases.
+   :term:`primary shard` for one or more databases.
 
    Issue the following command at the :program:`mongo` shell:
 

source/reference/command/movePrimary.txt

@@ -7,7 +7,7 @@ movePrimary
 .. dbcommand:: movePrimary
 
    In a :term:`shard cluster`, this command reassigns the database's
-   primary shard. The primary shard for a database holds all
+   :term:`primary shard`. The primary shard for a database holds all
    un-sharded collections in the database. :dbcommand:`movePrimary`
    is an administrative command that is only available for
    :program:`mongos` instances. Only use :dbcommand:`movePrimary` when

source/reference/glossary.txt

@@ -869,7 +869,7 @@ Glossary
       results. The optimizer then uses the query plan each time the
       :program:`mongod` receives the query. If a collection changes significantly, the optimizer
       creates a new query plan.
-      
+
    diagnostic log
       :program:`mongod` can create a verbose log of operations with
       the :option:`mongod --diaglog` option or through the
@@ -883,3 +883,7 @@ Glossary
 
       .. seealso:: :option:`mongod --diaglog`,
          :setting:`diaglog`, and :dbcommand:`diagLogging`. 
+
+   primary shard
+      For a database in which :term:`sharding` is enabled, the primary
+      shard holds all un-sharded collections.

source/tutorial/remove-shards-from-cluster.txt

@@ -23,7 +23,7 @@ To remove a shard, you will:
 
 - Move :term:`chunks <chunk>` off of the shard.
 
-- Ensure that this shard is not the "primary" shard for any databases
+- Ensure that this shard is not the :term:`primary shard` for any databases
   in the cluster. If it is, move the "primary" status for these
   databases to other shards.
 
@@ -97,9 +97,9 @@ Move Unsharded Databases
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
 Databases with non-sharded collections store those collections on a
-single shard known as the "primary" shard for that database. The
+single shard known as the :term:`primary shard` for that database. The
 following step is necessary only when the shard to remove is
-also the "primary" shard for one or more databases.
+also the primary shard for one or more databases.
 
 Issue the following command at the :program:`mongo` shell: