What is Fluid?
A fluid is a material or substance that will form and spread away if it is not contained by another material. Many people associate fluid with all liquid matter, when in fact gases are also classified as fluid substances. The water that we drink, the gasoline in our cars, and the water on rivers and oceans are all liquid substances and so are considered fluids. But on the other hand, gases that are present in the air are also considered fluids since these substances also continue to “flow” and deform in the atmosphere.

Based on molecular structure, those of fluids can freely move from each other. This is in contrast to the tightly-packed molecules of solid materials. This is the reason why most solids retain their shape even if some forces are applied. For a solid to be deformed, enough force must be applied to break down the link of molecules. The molecules on liquids on the other hand are not tightly bonded with each other and can be freely moved with little force. Using the example of water on a basin, if one pushes the water out of this container then it only requires little force for the water to be spilled over.

In the field of medicine and nutrition, fluids are most commonly associated with liquid intake of nutrients in the body. It is said that there is a minimum level of “fluid intake” for each person for his/her body to be functioning efficiently and to avoid certain medical conditions. In this sense, fluid points to the electrolyte composition in the body. When some substances and minerals are lacking in the body, an electrolyte or fluid imbalance may occur and this may lead to illness. To correct the imbalance of electrolytes in the body, increased fluid intake is usually advised by doctors and nutritionists.