Viscosity and rheology are often confused in the literature although they are significantly different concepts. The viscosity of a fluid or suspension is an indication of its fluidity. "Heavy" or "thick" fluids such as heavy oils, or molasses, are recognized as those having high viscosity. Water, many lubricating and cooking oils, coffee, and tea have low viscosities. Air is a fluid with very low viscosity. The rheology of a fluid or suspension, however, is an indication of the behavior of the viscosity as the fluid is sheared (or stirred) at different rates. Whipped cream is easy to stir, but it nevertheless can hold the spoon upright (or at some other odd angle) when not being stirred. This is an example of more complex rheology than simple fluids such as water or oil.