Update content/operate/rs/monitoring/db-availability.md

Author: rrelledge

content/operate/rs/monitoring/db-availability.md

@@ -41,7 +41,7 @@ To check database availability when using a load balancer and the recommended `a
 GET /v1/local/bdbs/<database_id>/endpoint/availability
 ```
 
-Returns HTTP status code 200 OK if all master shards are reachable from the local database endpoint.
+Returns HTTP status code 200 OK if all primary (master) shards are reachable from the local database endpoint.
 
 If the local database endpoint is unavailable, returns an error status code and a JSON object that contains [`error_code` and `description` fields]({{<relref "/operate/rs/references/rest-api/requests/bdbs/availability#get-endpoint-error-codes">}}).