Answer
Linear,
slope $=0$
Work Step by Step
A function is linear if there is a constant rate of change in the function's value, which is also called the slope.
Note that:
$8-8=0\\
8-8=0\\
8-8=0\\
8-8=0$
The difference of all consecutive $y$-values is $0$, which means that the slope is $0$.
Thus, the function is linear.