Structure wise fluid and liquid both as loosely held as compared to solid. But liquids contain the properties of water/oil. Whereas fluids are class of substances which have ease to flow. The major difference between liquid and fluid is liquids are incompressible (thereby generally used in hydraulics) whereas fluid is a generic term used for used for liquids as well as gaseous elements. Hence, some fluids (gaseous) are compressible but liquids are not. *ALL LIQUIDS ARE FLUIDS BUT ALL FLUIDS ARE NOT LIQUIDS* For example, water is liquid and atmosphere has fluid like properties.
