1. The problem asks for the coefficient of $y$ in the expression $5y + 8$. 2. The coefficient of a variable is the numerical factor that multiplies the variable. 3. In the term $5y$, the number $5$ multiplies $y$, so $5$ is the coefficient of $y$. 4. The term $8$ is a constant and does not affect the coefficient of $y$. 5. Therefore, the coefficient of $y$ in $5y + 8$ is $5$. **Final answer:** $5$