The natural point of departure for an editorial of a special issue on Human-Machine Communication (HMC) is the question of what HMC is. Addressing this question is not an easy task, as it is inherently linked to the more fundamental and general question of what communication is. The definition of communication, in turn, shapes the identity of an entire scholarly field and is thus subject to a vibrant and continuous debate. We do not aim at intensifying or complicating this debate but rather at providing an operational definition of HMC, which is merely supposed to serve as a framework for the special issue. Definition of human-machine communicationIn our view, communication can be regarded as the process of at least two entities "sharing" (Schramm 1954) something, suggesting an act of "bringing together" (Cobley 2008). These entities, in our context, are humans on the one hand, and machines or "digital interlocutors" (Edwards and Edwards 2017, p. 487) on the other hand. What they share is widely conceived of as messages or compilations of symbols. These messages are encoded, decoded and interpreted (cf. SchrammThe authors Katrin Etzrodt and Sven Engesser have contributed equally to this introduction.