To determine the type of number that results from the expression \( \sqrt{19} - \frac{3}{2} \), we can analyze each part:
- \( \sqrt{19} \) is an irrational number because 19 is not a perfect square.
- \( \frac{3}{2} \) is a rational number.
The result of an irrational number minus a rational number is still an irrational number. Therefore, the expression \( \sqrt{19} - \frac{3}{2} \) is an irrational number.
So the answer is: an irrational number.