Answer
Linear,
slope $=0.5$
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:
$-3.5-(-4)=0.5\\
-3-(-3.5)=0.5\\
-2.5-(-3)=0.5\\
-2-(-2.5)=0.5$
The difference of all consecutive $y$-values is $0.5$, which means that the slope is $0.5$.
Thus, the function is linear.