Our latest paper on the evolution of signal unreliability and deception has just been published in Animal Behaviour. Animal signals must allow receivers to make adaptive decisions better than they would in their absence. This fundamental tenet of animal communication hinges on the existence of a consistent relationship between the design of a signal and the functional information it makes available to receivers, but this leaves ample space for the evolution of deception and signal unreliability. In this paper, we argue that unreliability and deception are notions marred with conceptual ambiguities, often used as equivalent or as catch-all terms for qualitatively different processes. Signal unreliability refers to a pattern of design–information dissociation that can arise through different processes, some deceptive and some not, with different evolutionary implications. We point out (what we believe) are such misunderstandings and suggest adopting a theoretical framework explicitly based on the evolutionary scenarios leading to signal unreliability and deception, which has advantages over traditional schemes focusing exclusively on whether signals benefit receivers or not.