This volume presents a new reading of how ontology and language intertwine in Plato's thought. The main idea is that the structure of reality determines how language works. Conversely, analysing Plato's view on language is key to understanding his ontology. This work first focuses on Plato's standard theory of Forms and the plurality of functions they perform with regard to thought, knowledge and language. The volume then provides a detailed interpretation of the first definition of episteme as perception in Plato's Theaetetus, which is ultimately said to make language impossible. The main argument is that basic linguistic acts such as reference and predication rely on fundamental ontological grounds. Finally, the critique of the Theaetetus is connected to the complex account of true and false logoi in the Sophist. The result is a new interpretation of how language is connected to the ontology of kinds put forward in the Sophist, with particular regard to the nature of the kind Being. This book provides a detailed exegetical investigation into a crucial aspect of Plato's thought, which can also be of interest to those working in metaphysics and philosophy of language.