A "Newtonian fluid" is a term frequently used in fluid dynamics to describe a type of fluid behavior. However, there are several synonymous terms that can be employed to refer to this specific fluid nature. One common synonym is "viscous fluid", which indicates a fluid that displays consistent flow under varying pressure conditions, much like Newtonian fluids. Another equivalent term is "linearly viscous fluid", denoting a fluid that possesses a linear relationship between shear stress and shear rate. Additionally, the term "simple fluid" may be used interchangeably with Newtonian fluid, emphasizing the straightforward behavior and absence of complex flow patterns. These synonyms allow researchers and scientists to emphasize different aspects of the behavior of these fluids while referring to the same core concept.