Answer:
lol... it depends
Explanation:
The function is how something works and the Relation is something that is similar or (root word) 'related' to that something.
The difference between and function and a relation is the object itself. The function of the object will always be different from the relation that another object has to it.
The similarities of the function and relation of an object would be its purpose. If you were learning about the function of a cheese grater and the similarity with a zester its (one) the look of it and to the purpose.. which would be to shred and Zest.. pretty self explainatory right?