1. **State the problem:** We need to determine if the statement "If $n$ is even and $a$ is negative, then the $n$th root of $a$ is not a real number" is true or false. 2. **Recall the definition:** The $n$th root of a number $a$ is a number $x$ such that $x^n = a$. 3. **Important rule:** When $n$ is even, the $n$th root of a negative number $a$ is not a real number because raising any real number to an even power results in a non-negative number. 4. **Example:** For $n=2$ (square root) and $a=-4$, there is no real number $x$ such that $x^2 = -4$. 5. **Conclusion:** Therefore, the statement is **true**. The $n$th root of a negative number is not real if $n$ is even.