>[!abstract] >Lehmann's Laws of Software Evolution, formulated by Manny Lehman, are a set of principles describing how large, long-lived software systems behave over time. Based on empirical study, they state that such systems must continually evolve or become less useful (continuing change), their complexity tends to increase unless actively reduced (increasing complexity), and their evolution is subject to organizational, social, and resource constraints (self-regulation). Additional laws describe tendencies toward conservation of familiarity, growth, and system decline if maintenance lags. Together, they frame software not as static artifacts but as evolving socio-technical systems, highlighting why long-term sustainability requires ongoing adaptation and management. >[!related] >- **North** (upstream): [[Software evolution theory]] >- **West** (similar): [[Conway's Law]] >- **East** (different): [[Ossification]] >- **South** (downstream): —