It could be this marker, it could be this whiteboard, it could be me, it could be the room, the building, this system. For example, if we chose this eraser to be the system has certain properties, it has a certain weight, it has a certain mass, it has a certain volume, certain density, certain pressure, certain height, length and width. It has certain properties that are used to quantify this system. And these properties, if you list them all in order, could be subdivided into two categories extensive properties and intensive properties. Okay? Extensive properties are those properties that depend on size and intensive properties do not depend on size.