Identify the expression to evaluate: the negative square root of 121, written as \(-\sqrt{121}\).
Recall that the square root symbol \(\sqrt{\cdot}\) represents the principal (non-negative) square root of a number.
Calculate the square root of 121 by finding the number which, when squared, equals 121. This means solving \(x^2 = 121\) for \(x\).
Since 121 is a perfect square, determine its positive square root value.
Apply the negative sign in front of the square root to get the final expression: \(-\sqrt{121}\) equals the negative of the positive root found in the previous step.