This volume presents a range of studies testing some of the latest models and hypotheses in the field of second/third language acquisition, such as the Bottleneck Hypothesis (Slabakova, 2008, 2016), the Scalpel Model (Slabakova, 2017), and the Interface Hypothesis (Sorace & Serratrice, 2009) to name a few. The studies explore a variety of linguistic properties (e.g., functional morphology, linguistic properties at the syntax-discourse interface) by focusing on distinct populations (L2 acquisition, L3/LN acquisition, Heritage Speakers), while also considering the links between experimental linguistic research, generative linguistics, and, in some cases, language pedagogy. Dedicated to Roumyana Slabakova, each chapter can be directly linked to her work in terms of the empirical testing of extant hypotheses, the formulation of new models and ideas, and her efforts to advance the dialogue between different disciplines and frameworks. Overall, the contributions in the volume bear evidence of Slabakova's enduring influence in the field as a collaborator, teacher, and researcher.