Imagine that in a distant galaxy there is a planet just like Earth, except for one tiny detail: there is no H2O on this planet. The clear, drinkable liquid which fills the lakes and rivers of this
Imagine that in a distant galaxy there is a planet just like Earth, except for one tiny detail: there is no H2O on this planet. The clear, drinkable liquid which fills the lakes and rivers of this planet is not H2O, but a different chemical, XYZ.
Imagine that two different chemicals can sometimes have the same surface properties: they can look, taste, smell, and behave the same. XYZ quenches thirst like H2O, it tastes and smells like H2O, and the people on this planet call it "water".