👉 Fluid, in its broadest sense, encompasses all substances that flow or deform under applied stress, ranging from liquids and gases to semi-solid materials like mud and polymers. Liquids, such as water or oil, are characterized by their ability to take the shape of their container while maintaining a constant volume, with molecules held together by intermolecular forces but free to move past one another. Gases, like air or hydrogen, exhibit high compressibility and occupy a significant volume, with molecules moving rapidly and independently. Semi-solid fluids, or viscoelastic materials, like polymers or certain biological tissues, exhibit properties of both liquids and solids, displaying both viscous flow and elastic deformation. The behavior of fluids is governed by fundamental principles such as fluid dynamics, which studies the motion of fluids and the forces acting upon them, and fluid statics, which deals with fluids at rest. Understanding fluid behavior is crucial in various fields, including engineering, meteorology, and biology, where it influences everything from the design of pipelines to the understanding of weather patterns.
