In design, human-computer interaction, and software development, interaction design, often abbreviated IxD, is "about shaping digital things for people's use", alternately defined as "the practice of designing interactive digital products, environments, systems, and services." Like many other design fields interaction design also has an interest in form but its main focus is on behavior.

What clearly marks interaction design as a design field as opposed to a science or engineering field is that it is synthesis and imagining things as they might be, more so than focusing on how things are.