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It is '''very important''' to understand that, by calling a thermodynamic property a '''property''', it is implied that it belongs to the substance. It does '''not''' depend on the way you look at it, or, in physical language, it is independent of the frame of reference. For example, when you stand still you think the air is still stationary at a temperature of 25°C, but if you drive past in a car you will think the air is moving. This does not, however, affect the fact that the air is still at 25°C. We shall see later that we can define some other things that depends on motion, known as the stagnated stagnation '''quantities''', sometimes incorrectly referred to as "stagnation properties".