Aristotle's Categories remains one of the foundational works in the history of Philosophy. At the foundations of all human thought and argument is the precise understanding of our words, and in his Categories, Aristotle proves to be a master unsurpassed in providing the tools necessary for defining our words and understanding the things signified by them. Nevertheless, the Categories is a text which is at times obscure and difficult to understand for a modern student. Therefore, we have provided this volume to remedy the difficulties a modern student may have in understanding the Categories. Written in clear style, this line-by-line explanation of the Categories alternates between a universal overview and division of the text and a detailed question and answer format which raises many of the questions modern students have about difficult passages. Liberal use is made also of the ancient Greek and Latin commentators on the Categories.