The chapter defines the concept of approach, along with its derivation and exemplification. A general definition of approach is proposed. The latter is then applied to HCI research in particular. An approach to HCI comprises the addressing of the topic or problem of human–computer interaction research; the performing of actions to progress the approach to the addressing of the topic or problem of human–computer interaction research; the evaluating of the success of the actions performed to progress an approach to the addressing of the topic or problem of human–computer interaction research; and the cumulating of the successes of whether the topic or problem of human–computer interaction research has been addressed or not. The definition is both explicit and sufficiently well specified for the later application of frameworks to the approaches, retained here – innovation, art, craft, applied, science and engineering.