Definition
Software entropy is the principle that a codebase, left to itself, tends toward greater disorder. Borrowed from thermodynamics, the term names the way structure degrades as a project accumulates patches, shortcuts, and inconsistent decisions. The result is often called code rot: a system that becomes progressively harder to understand and change.
Entropy is not caused by a single dramatic failure. It builds up through many small compromises, each individually defensible, that together erode the clarity of the design. Over months, a clean architecture becomes a tangle that no one fully trusts.
Why it matters
How it works
The classic illustration is the broken window. One unrepaired broken window in a building invites more vandalism, because it signals that no one is paying attention. A neglected bug, an ugly workaround, or a poorly named module sends the same message inside a codebase: standards have slipped, so further sloppiness feels acceptable.
Fighting entropy means repairing small damage promptly rather than letting it sit. Refactoring, removing dead code, fixing warnings, and keeping naming consistent are all entropy-reduction work. None of these tasks ships a feature, but each one keeps the system in a state where future features remain cheap to add.