1. The problem is to understand the relationship between $-\sqrt{2}$ and $\sqrt{2}$. 2. Recall that $\sqrt{2}$ is the positive square root of 2, approximately 1.414. 3. The negative sign in front of $\sqrt{2}$ means $-\sqrt{2}$ is the negative counterpart, approximately -1.414. 4. On the number line, $-\sqrt{2}$ is to the left of zero, and $\sqrt{2}$ is to the right of zero. 5. Therefore, $-\sqrt{2}$ is less than $\sqrt{2}$, or $-\sqrt{2} < \sqrt{2}$. 6. This means $-\sqrt{2}$ is "under" or less than $\sqrt{2}$ in value.