To solve the problem of evaluating the permutation expression \({ }_{18} \mathrm{P}_{0}\), we use the formula for permutations, which is given by:
\[
{ }_{n} \mathrm{P}_{r} = \frac{n!}{(n-r)!}
\]
In this case, \(n = 18\) and \(r = 0\). Substituting these values into the formula, we get:
\[
{ }_{18} \mathrm{P}_{0} = \frac{18!}{(18-0)!} = \frac{18!}{18!} = 1
\]
The formula for permutations is given by:
\[
{ }_{n} \mathrm{P}_{r} = \frac{n!}{(n-r)!}
\]
In this problem, we have \(n = 18\) and \(r = 0\). Substituting these values into the permutation formula, we get:
\[
{ }_{18} \mathrm{P}_{0} = \frac{18!}{(18-0)!} = \frac{18!}{18!}
\]
Since \( \frac{18!}{18!} = 1\), we find that:
\[
{ }_{18} \mathrm{P}_{0} = 1
\]