What is the absolute value of -4?

The absolute value of a number is defined as its distance from zero on a number line, regardless of the direction. Therefore, the absolute value is always a non-negative number. When determining the absolute value of -4, we are looking for how far -4 is from zero, which is 4 units. Since absolute values cannot be negative, the correct answer is indeed 4. This understanding is fundamental in mathematics, as it applies to both positive and negative numbers, ensuring that all calculations reflect the magnitude without concern for sign.