Property

Every property has two elements: a name and a value. The name of a property can never be used without its associated value. A property without its value is meaningless. To say that something has mass without saying how much mass is wrong.

Property and value form not just any pair but what is called an ordered pair: (property, value). The pair (property, value) is not the same as (value, property); the order matters, and in this relation the first member is always a property and the second is its value. A value alone is just a number with units; a property name alone is just a word.

Consider water. The first thing most people will say about it is "it is H₂O," thinking they are displaying their chemical knowledge. But H₂O is not a property of water. It is an alternate name. What property of water has a value of H₂O? The property of composition. Water's composition has the value H₂O; composition is the property, H₂O is the value. The same trap waits with mass. As soon as you say water has mass, you must include how much mass. Water has A mass: 25 grams, 1000 grams, 250 milligrams. The concept "water" does not have the property of mass; only this water, here, in this glass, does.

This is why describing a thing requires more than naming its features. A feature is something a thing has; a property is what we say about that feature, in a particular case, with a particular value. Without the value, the property is unfinished, a sentence with no predicate. The discipline of always saying both is what separates describing the world from gesturing at it.