Why are liquids and gases categorized as fluids?

The state of various substances to categorize as solid, liquid or gaseous depends on the nature of the constituent particles and the interactions and bonding between them. Liquids and gases are categorized as fluids because The liquid and gases have a property to flow i.e the molecules can move past and tumble over one another freely. The molecules in these two substances are free to move about unlike solids who are rigidly placed in their position and can only oscillate.