A smart fluid is a dynamic material that can change its viscosity, flow and shape in response to external stimuli such as temperature, pressure or magnetic field. There are several synonyms for the term smart fluid, such as intelligent fluid, active material, and adaptive material. These materials have unique properties that make them ideal for a wide range of applications, such as drug delivery systems, energy harvesting devices and flexible electronics. Some other synonyms for smart fluids include responsive fluids, tuneable fluids, and controllable fluids. These advanced materials are revolutionising the way we think about fluid mechanics and have opened up new avenues for research and development in areas such as biotechnology and nanotechnology.