Computational Processes vs. Organizational Processes in a workflow

At the very beginning of this Wikipedia page on Activity Diagram, it says:

Activity diagrams are graphical representations of workflows of stepwise activities and actions with support for choice, iteration, and concurrency. In the Unified Modeling Language, activity diagrams are intended to model both computational and organizational processes (i.e., workflows), as well as the data flows intersecting with the related activities.

The referenced link describes the term computational and organizational processes in detail. However, the Wikipedia page on Workflow doesn't touch the term computational processes.

So my question is: Is the term workflow only limited to organization processes or does it include both organizational and computational processes?

I want to understand the definition of workflow in relation to the activity diagram.

The power of activity diagram

First of all, according to UML specifications:

An Activity is a Behavior specified as sequencing of subordinate units, using a control and data flow model.

This is a powerful tool, which can be used for describing behaviours of systems. Now, what kind of system is left open to the user:

• UML was probably designed with primarily IT systems in mind.
• But most of its tools were successfully used to describe organisational systems (i.e. people working together, with or without IT) and in particular companies using IT systems. The best example is Ivar Jacobson's book "The object advantage: business process reengineering with object oriented technology". Ivar is one of the co-inventor of UML, btw.
• I have not tried, but I suspect that it could be used to model behavior of any kind of systems, such as social systems, biological systems an organisational system, and why not a social or a biological system. Just have a read of Herbert Simon's "Science of the artificial" to get inspired.

What does UML say on workflows?

UML is neutral on its domain of use. And UML does not define "workflow". The specification mentions this term only in a few diagram examples and in this sole paragraph:

Activities may describe procedural computation, forming hierarchies of Activities invoking other Activities, or, in an object-oriented model, they may be invoked indirectly as methods bound to Operations that are directly invoked. Activities may be applied to organizational modeling for business process engineering and workflow.

(The term computation is not necessarily related to computing machines. Keep in mind that in the fifties, the term computer was also used to refer to people doing computations (see NASA article)).

Is there any other suitable definition of workflow

There is no authoritative definition of workflow as far as I know. The term is common business language, for example in the Cambridge dictionary defines it as:

the way that a particular type of work is organized, or the order of the stages in a particular work process

Workflows refer to organisation processes, software processes, but most often a combination of the two.

There is a Workflow management coalition who has established a number of workflow "standards". They have defined a term, but it is restricted to their own domain of application, i.e. in relation with automation.