"Negative One" refers to the number that is one less than zero. In mathematics, it is represented as -1 and is part of the set of integers. This number is important because it helps us understand concepts like debt or loss, where having less than nothing can be represented by negative values. In everyday life, we might encounter -1 when discussing temperatures below freezing or when calculating scores in games. For example, if a team loses a point, their score might drop to -1. Understanding negative numbers, including -1, is essential for various real-world applications, from finance to science.