How do you explain technical and professional communication? The field has long tried to answer this question, with limited success. Because the field is constantly evolving alongside social, technological, and communication changes, it remains difficult to explain. Assembling Critical Components presents TPC as a collective identity and provides a framework for situating critical components of the field. This collection includes chapters reflecting on topics such as accessibility, professional communication, regulatory writing, socio-technical situation, procedural knowledge, applied rhetoric, and ethics. These topics are contextualized by entries presenting field-wide data on topics including influential texts, key terms, and teaching practices over time. Assembling Critical Components provides students, teachers, researchers, program administrators, and industry professionals a tangible yet flexible approach to explaining TPC.