#### Answer

-1

#### Work Step by Step

In order to calculate the larger powers of $i$, we can first calculate the values of $i$, $i^{2}$, $i^{3}$, and $i^{4}$.
$i^{1}=i$
$i^{2}=i\times i=-1$
$i^{3}=i\times i^{2}=i\times-1=-i$
$i^{4}=i^{2}\times i^{2}=-1\times-1=1$
We can use these values and the rules of exponents to derive larger powers of $i$.
Therefore, $i^{18}=i^{16}\times i^{2}=(i^{4})^{4}\times i^{2}=1^{4}\times-1=1\times-1=-1$.