Fungible - which derives from the Latin verb fungi, meaning "to perform (no relation to the noun "fungus" and its plural "fungi") - is a word that often shows up in legal contexts. Something fungible can be exchanged for something else of the same kind. For example, we could say "oil is a fungible commodity." That means that when a purchaser is expecting a delivery of oil, any oil of the stipulated quantity and quality will usually do. Another example of something fungible is cash. It doesn't matter what twenty dollar bill you get - it's still worth the same amount as any other twenty dollar bill. In contrast, something like a painting isn't fungible; a purchaser would expect a specific, identifiable item to be delivered. In broader use, "fungible" can mean "interchangeable" or sometimes "changeable, fluid, or malleable."