What encompasses the definition of a set of changes a user can make at once?

The definition of a set of changes a user can make at once is best captured by the term "action." In the context of user interfaces and interaction design, an action refers to any operation or command that a user can initiate, leading to changes in the system or application state. This can include modifying multiple settings, submitting a form with several inputs, or executing a batch process. The essence of an action is that it allows users to perform a specific task that results in one or more alterations occurring simultaneously.

In contrast, affordance refers to the attributes of an object that suggest its functionality and how it can be interacted with, rather than the changes that can be made. An object set involves a collection of items being referenced or manipulated, but it does not specifically encapsulate the concept of making changes in an interactive manner. Submission criteria outline the conditions that must be met for a submission to be processed but do not directly describe the act of executing a series of changes simultaneously. Hence, "action" is the most fitting term to describe the set of changes a user can make at once.