diff --git a/source/core/replication-introduction.txt b/source/core/replication-introduction.txt
index ccbc9350953..fa49725710a 100644
--- a/source/core/replication-introduction.txt
+++ b/source/core/replication-introduction.txt
@@ -54,7 +54,7 @@ the primary, however, clients can specify a :doc:`read preferences
 
 .. include:: /images/replica-set-primary-with-two-secondaries.rst
 
-You may add an extra :program:`mongod` instance a replica set as an
+You may add an extra :program:`mongod` instance to a replica set as an
 **arbiter**. Arbiters do not maintain a data set. Arbiters only exist
 to vote in elections. If your replica set has an even number of
 members, add an arbiter to obtain a majority of votes in an election