Definitions of scope: data, knowledge
Knowledge visualization vs data visualization: for the terms of design, both are variations of content to be visualized. For data, we will understand statistical data ; for knowledge, everything explained that is not statistical. Although somehow arbitrary, this will be a practical guideline.
UX User Experience): the perception of the user trough the whole interaction or consumption of the product/visualization. Related: User journey, pain points.
UI (User Interface): the visual/haptic/aural design that is the main channel for interaction (mainly in a screen)
Information Theory: A theory about how information works, mainly used for computational purposes, but broader in the scope of applications. Term coined by Claude Shannon.
Information Architecture: The organization of the information for the use. Examples of use include the distribution of information in a web site trough its many levels and also the organization of the flow of information in a computer network. Related terms: taxonomy
HCI: Study of Human Computer interaction. Related to ergonomics