Does scarcity apply only to commodities?
For completeness, you might want to include the definition of Fungibility as well:  "In economics, fungibility is the property of a good or a commodity whose individual units are essentially interchangeable, and each of its parts is indistinguishable from another part."

If you have a collection of objects, and each object is (in some relevant sense) interchangeable with any of the other objects, then they are fungible and thus a commodity.  If there aren't very many of them, they may be scarce.

However, if you have a collection of objects, none of which are interchangeable with any others in a relevant sense, then they are essentially unique objects.  You could still say that they were scarce (there is only one of each) but not that they are commodities... though in practice, people typically don't refer to unique objects as scarce.