The drag coefficient refers to the measure of resistance that gases or fluids exert when an object moves through them. Some synonyms for this term include drag force, aerodynamic drag, and air resistance coefficient. The drag coefficient is an important factor for engineers and aerodynamicists when designing aircraft, cars, and other vehicles, as minimizing drag can significantly improve fuel efficiency and performance. Other related technical terms include the lift-to-drag ratio, which describes the efficiency of an aircraft in generating lift versus the drag it experiences, and the Reynolds number, which relates to the type of airflow around an object. Understanding these concepts is crucial for optimizing the design and performance of various transportation systems.