This book explores grammatical structures that have traditionally been marginalized in linguistic studies. The reasons for such neglect are multiple: in part it could be due to low frequency or low productivity, but it is also because the data so often stem from underrepresented languages. The chapters in this volume contribute detailed case studies underlining the importance of marginal grammatical structures in advancing empirical and theoretical research, as well as extending the boundaries of knowledge in the field. The volume is intentionally diverse in three ways. First, it is empirically rich, in that it includes data both from traditionally understudied languages, such as the Australian languages Pintupi-Luritja and Iwaidja, the Ethiopian language Amharic, the Middle Eastern language Aramaic, and the Indic language Romani, as well as from better-studied languages such as Chinese, English, and Spanish. Second, it brings together contributions from several subdisciplines, namely morphology, syntax, and semantics, including diachronic and typological perspectives. Third, the volume is theoretically varied, which provides the reader with evidence of how different frameworks and approaches, as well as emerging digital tools and methods, can incorporate marginalized data in their discussions. The volume as a whole aims to expand the scope of linguistic inquiry and to advance our knowledge about what counts as linguistic evidence, a key question for fundamental and empirical linguistic investigation.