The functional domain of apprehensionality encompasses grammatical markers or constructions which conventionally encode or pragmatically implicate that the situation described by the clause is an undesirable possibility. Its main manifestations discussed in this volume are (i) apprehensives, which are modal markers which can occur in main clauses, and thus could serve to translate English might in Don't go near this dog, it might bite (but also add a component of undesirability), and (ii) precautionary subordinators such as English lest in Don't go near this dog, lest it bite. As just illustrated, such elements tend to occur in warnings and are often but not necessarily accompanied by an instruction as to how to avoid the undesirable situation. Although wide-spread cross-linguistically, they have received very little attention in the linguistic literature and their discussion has been mostly restricted to brief sections in language-specific discussions of some lesser studied languages. This volume addresses this gap by presenting in-depth discussions of apprehensional markers in individual languages (and in some contributions, language groups), by experts on these languages and based on first-hand data. The editors' introduction offers a review of the existing literature, including of the varied terminology used and of the main research questions arising. The individual papers present detailed investigations of the semantic and pragmatic properties of the construction(s) in question, their syntactic status, and in many cases also their diachrony. The final contribution is a questionnaire for the in-depth exploration of variation within apprehensional constructions. The volume is aimed at typologists, semanticists interested in modality, and general linguists.