In software engineering, quality is the degree to which a system, component, or process meets specified requirements and customer/user needs and expectations. It is often decomposed into attributes such as functionality, reliability, usability, efficiency, maintainability, and portability (ISO/IEC 25010).
Quality is the single biggest predictor of long-term software viability. Low quality leads to "brownout"—where technical debt consumes all engineering capacity, bringing feature velocity to zero. High quality enables sustained agility.
Quality is not something you add; it is the absence of waste. We define quality not just by the absence of bugs, but by the elegance of the architecture and the clarity of the code. Code that works but is unreadable is low quality.