The Maintainability Index is a quantitative measure used to evaluate how easy it is to maintain and modify software. It combines various factors, such as code complexity, documentation quality, and the number of lines of code, to produce a single score. A higher score indicates that the software is easier to maintain, which can lead to reduced costs and improved efficiency over time. This index is particularly useful for software developers and project managers, as it helps identify areas that may require refactoring or additional documentation. By focusing on maintainability, teams can enhance the longevity and adaptability of their software, ultimately benefiting users and stakeholders alike.