👉 Fluid refers to a substance that can flow or change shape in response to external forces, unlike rigid solids or gases. This property is characteristic of liquids but can be observed in some other states of matter as well. In a fluid, molecules are closely packed but not tightly bound, allowing them to move past one another while still maintaining cohesion. This results in the ability of fluids to fill the shape of their container and exhibit surface tension, where molecules at the surface experience a net inward force. Variations in fluid behavior can be seen in different states of matter, such as water in its liquid state, which can flow and take the shape of its container, or in gases, which can expand to fill any space but lack a definite shape.
