Relation 2 \begin{tabular}{|c|c|} \hline Domain & Range \\ \hline 8 & pen \\ \hline 8 & star \\ \hline 8 & pencil \\ \hline 8 & sky \\ \hline 8 & rock \\ \hline \end{tabular} Function Not a function

Step 1 ：Given the relation 2 with the following pairs: (8, pen), (8, star), (8, pencil), (8, sky), (8, rock).

Step 2 ：In a function, each element in the domain must map to exactly one element in the range.

Step 3 ：Here, the element '8' in the domain is mapping to multiple elements in the range: 'pen', 'star', 'pencil', 'sky', 'rock'.

Step 4 ：Therefore, the given relation is not a function.

Step 5 ：Final Answer: The given relation is \( \boxed{\text{not a function}} \).