DOCSP-1495: sentence improvement

Author: schmalliso

source/core/replica-set-oplog.txt

@@ -22,8 +22,8 @@ contain a copy of the oplog, in the :data:`local.oplog.rs` collection,
 which allows them to maintain the current state of the database.
 
 To facilitate replication, all replica set members send heartbeats
-(pings) to all other members. Any member can import oplog entries from
-any other member.
+(pings) to all other members. Any :term:`secondary` member can import
+oplog entries from any other member.
 
 Each operation in the oplog is :term:`idempotent`. That is, oplog
 operations produce the same results whether applied once or multiple