Fungibility

Fungible

Some things that are fungible:

Money (my dollar is the same as your dollar)
Commodities (by definition)
Concert tickets (at least within the same tier)
Calories (your body doesn't care if you eat a beautifully presented burger, drink it as a blended burger slushy)
Game scores (the points may be fungible, but your rank on the leaderboard is not)

Some things that are non-fungible:

Realestate (even if we had two identical houses, they could not occupy the same space so their properties would be different -- perhaps one has the corner lot, or more trees, worse neighbours)
Identity (the thing that makes you different from other people)
Web addresses and domains, email addresses, driver's license (arguably things that make up your identity)
Relationships (your friendship with Alice is not the same as Bob's friendship with Alice)

Some things are both?

Limited edition art (the number of instances within the edition can be fungible, but the collection itself is non-fungible)
Multi-tier concert tickets (fungible within tiers, but not fungible across tiers)
Credentialism (limited set of people who match some criteria)
In general, these are non-fungible groups of fungible things

Can we take non-fungible things and make them fungible?

Realestate Investment Trust (REIT) are collections of realestate investments that give shareholders fungible partial ownership. One share in a given REIT is the same as another share in the same REIT, despite the REIT being composed of non-fungible assets.
Holding companies can issue fungible shares to the ownership of a single non-fungible asset, such as a building co-op where tenants are equal owners.

Can fungible things become non-fungible?

Tainted money (sanction against specific provenance of sequenced bills or asset transfers can make more difficult to liquidate, thus reducing their face value)
Damaging or destroying an asset can reduce its value relative to the rest of the collection (such as burning a dollar, or creasing a limited edition comicbook)
Unique provenance can change the value of a commodity relative to other equivalent assets (such as buying a used car that was allegedly previously owned by a celebrity)