Interaction Design aims to integrate the physical and cognitive product interface into a successful whole in order to create understandable, usable and enjoyable computer-based products. - Institute for Design
Human Computer Interaction is considered quite broadly as "design for human use." - Stanford HCI class
Interaction design is the process of producing useful, usable, and desirable software products. - Brad Weed, Microsoft
Interaction design is a way of comparing and understanding how different kinds of experiences can be developed to support the goals and messages of any communication. - Nathan Shedoff
Interactivity isn't about non-linear navigation or moving animations on the screen. It's about what people can do on the site, what they can participate in, what the site does to address their needs, interests, goals, and abilities.
Interaction is not animation. It's not audio. It's not video. It's "user control and dynamic experience." - Terry R. Schussler
By interaction we mean any communication between a user and computer, be it direct or indirect. Direct interaction involves a dialog with feedback and control throughout the performance of the task. Indirect interaction may involve background or batch processing. The important thing is that the user is interacting with the computer in order to accomplish something. -The Essential Guide to User Interface Design
Rather than designing sidebars and menus, you're designing spaces and interactions. In short, you're crafting the user experience. . . . In the graphical environment of the Web, interface design has to do with constructing visual meaning. The happy marriage of architecture and interface -- of logical structure and visual meaning -- creates a cohesive user experience. -Jennifer Fleming