[commonlisp94]

> Relations are functions.

That is how they are defined in set theory based math. The mathematical definition is not the only meaning of a word. When when start to talk about the physical world, we need additional concepts. You are welcome to read the wikipedia page about correspondence theories of truth.

[ukj]

The fact is you are talking about the meaning of words. Be they English words; or Mathematical words.

If you are going to talk about the correspondence theory in the same breath as you are talking about any language - you need to solve the symbol-grounding problem.

What function/mechanism/relation (or if you don't like any of those words - pick your own) grounds symbols?

https://en.wikipedia.org/wiki/Symbol_grounding_problem