Relation 4 \[ \{(-6, c),(1, m),(-1, e),(8, u)\} \] Function Not a function

Step 1 ：The problem is asking whether the given relation is a function or not. A relation is a function if for every input there is exactly one output. In other words, no two pairs in the relation should have the same first element.

Step 2 ：Looking at the given relation \[ \{(-6, c),(1, m),(-1, e),(8, u)\} \], we can see that all the first elements of the pairs are distinct.

Step 3 ：Therefore, the given relation is a function.

Step 4 ：Final Answer: The given relation is a \(\boxed{\text{function}}\).