A Definition of Decision Support

The term decision support, if my knowledge of history of this area is correct, goes back to the 1970s when it was coined by some academics associated with the Massachusetts Institute of Technology. Since then, many academic definitions have been offered. - My purpose in this essay is to provide a definition that may lend clarity to practitioners.
A decision support system or tool is one specifically designed to allow business end users to perform computer generated analyses of data on their own.

I believe the essence of decision support is, in the language of the 1960s, to allow end users to do their own thing. I note that this definition is still fuzzy because what constitutes analyses and "on their own" are debatable points.
We cannot say that decision support systems or tools necessarily support the making of decisions.

What's in a name? - As far as I know, cognitive researchers do not agree on how decisions are made. Therefore, saying that these tools support making decisions is not a provable statement. Nor, is it, in may opinion, an insightful way of defining these tools.
These tools do not analyze by themselves - rather they help a person analyze.

In other words, the tools facilitate analyses rather than perform analyses. If you want to learn more about how the tools facilitate analyses, see my essay on What Decision Support Tools are Used For.
Data warehousing and decision support systems and tools do not necessarily go hand in hand.

Many data warehouses are not used as decision support systems. And decision support systems or tools do not necessarily require the use of a data warehouse as a source for data. I assert that, by far, the most used decision support tools are spreadsheets not connected in any automated way with a data warehouse.
Business intelligence seems to have become the vendors' preferred synonym for decision support.

My guess is because decision support has an academic connotation and, as just mentioned, decision support systems do not necessarily support decisions. On the other hand, business intelligence systems do not necessarily make a business more intelligent. By the way, the consultant-coined term business intelligence goes back to the late 1980s, fell out of use, and then was revived by the DW/DSS world in the late 1990s. Confusingly, business intelligence is also used as a synonym for competitive intelligence (and is probably a more apt term for that area). By the way, "analytics" seems to be an up and coming name for this area - despite the mid-1990 consultant-coined term "analytical applications" never taking hold.