Some of the definition of fluid.......
A fluid is defined as a substance that continually deforms (flows) under an applied shear stress
regardless how small the applied stress.
A liquid or gas that flows and assumes the shape of its container.
Any substance that cannot retain the shape of its container once removed from the container. So gases and liquids are considered as fluids.
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A continuous amorphous substance that tends to flow and to conform to the outline of its container: a liquid or a gas capable of flowing and easily changing shape
