To evaluate the expression \( \sqrt{19} - \frac{3}{2} \), we first note that:
- \( \sqrt{19} \) is an irrational number because 19 is not a perfect square.
- \( \frac{3}{2} \) is a rational number.
Now, when you subtract a rational number ( \( \frac{3}{2} \) ) from an irrational number ( \( \sqrt{19} \) ), the result will always be irrational. This is because the set of rational numbers does not contain any irrational numbers, and subtracting a rational number from an irrational number cannot "cancel out" the irrationality.
Therefore, the result of the expression \( \sqrt{19} - \frac{3}{2} \) will be an irrational number.