system
Given the following post, respond as if you're commenting on Reddit:
human
Gases and liquids are fluids, but solids aren’t. Does plasma, the fourth state of matter, count as a fluid?

Most of my search results are giving me information on blood plasma, and I’m not finding a clear yes or no about the kind of plasma I actually want to know about. Is the definition of fluid absolutely applicable to plasma the same way it is for liquids and gases, or is it just used as a theoretical condition to lay down a framework for studying its behavior? Or, is it a “yes, but more complicated” situation kind of like how light is both a particle and a wave?
gpt
Plasma is absolutely a fluid, and in e.g. astrophysics simulations we use the same equations of hydrodynamics to describe it. Plasma is really just ionised gas. It can behave differently to a non ionised gas, especially in how it interacts with magnetic fields, which is why we have fields like *magnetohydrodynamics*, but even there this still counts as a sub field of hydrodynamics, i.e. fluid dynamics.