The number −1 (negative one) is an integer that represents a value less than zero. In mathematics, negative numbers are used to indicate a deficit or a loss. For example, if you have a balance of −1 in your bank account, it means you owe one unit of currency. Negative numbers, including −1, are essential in various fields such as algebra, finance, and physics. They help in solving equations, managing debts, and representing temperatures below zero. Understanding negative numbers is crucial for grasping more complex mathematical concepts and real-world applications.