A normal-shock inlet is a type of flow where a shock wave is formed perpendicular to the flow direction. It is an important phenomenon in the study of fluid dynamics, particularly in aerodynamics. There are various synonyms that can be used to describe this phenomenon, including normal shock wave, oblique shock wave, bow shock, and shock front. These terms all refer to the same basic idea of a sudden change in flow velocity caused by a shock wave. Understanding the behavior of normal-shock inlets is important in designing aircraft and other vehicles that must move through a fluid medium.