👉 Fluid, in its most basic sense, refers to any substance that can flow or change shape without breaking into distinct parts. This concept encompasses a wide range of materials, from liquids like water and oil to more complex fluids such as blood, magma, and even certain gases. The key characteristic of fluid substances is their ability to deform under applied stress and return to their original shape when the stress is removed, a property known as viscosity. This behavior can vary greatly depending on the fluid's composition and conditions such as temperature and pressure. For instance, water is a liquid at room temperature but can behave differently under extreme conditions, like supercritical fluids, which exhibit properties of both liquids and gases. Thus, fluidity is a versatile concept that describes the dynamic nature of many substances in various states and environments.
