Can 'clustering' and 'alwayson failover clustering' be used interchangeably?
&quot;Clustering&quot; is definitely used here to refer to SQL Server's Failover Cluster Instances (FCIs). However, the terms are not interchangeable.
Both FCIs and Availability Groups (AGs) are built on top of Windows Server Failover Clusters (WSFCs). I've seen FCIs, AGs, and WDFCs referred to as &quot;Clusters&quot; or &quot;Clustering.&quot;  The correctness of referring to any of these simply as &quot;Clustering&quot; is debatable.
What isn't debatable is that referring to any of those technologies simply as &quot;Clustering&quot; is ambiguous and can be confusing without proper context. Using the more verbose terminology, or even in abbreviations will always be unambiguous.