Every property has two elements: a name and a value. The pair is ordered: the name comes first, the value second. A property without its value is meaningless, and a value without a name to belong to is just a number.
Name and value form what is called an ordered pair. Mass and 25 grams are not the same as 25 grams and mass; the order tells you which is the description and which is the quantity. The first member of the pair is always a property; the second is always its value. Take either away and what remains is not a property.
We sometimes write properties as a parenthesized pair: (mass, 25 grams), (color, red), (state, solid at room temperature). The notation is just a reminder that the two elements travel together. To say a thing has mass tells us nothing useful. To say a thing has 25 grams of mass tells us something we can compare, conserve, and reason about.
The discipline of always writing the value alongside the name is what separates a description that has substance from one that gestures. A column of property names is a list. A column of name-and-value pairs is a description of the world.
Question
Are (mass, 25 grams) and (25 grams, mass) the same?
Reveal Merrill's answer →Hide answer
No. The pair is ordered; the first member is always the property name and the second is always its value. The order tells you which is the description and which is the quantity. (mass, 25 grams) is a property. (25 grams, mass) is a confused statement.