Software bug

A software bug is an error, flaw, or fault that makes a program behave incorrectly, unexpectedly, or contrary to its intended design.

Software defect: A flaw in a software artifact that can cause failures when the software runs. A defect in code or design is a common underlying source of a bug.
Debugging: The process of locating, understanding, and correcting defects in software. Debugging turns an observed bug into a traced cause and a repair.
Ariane 5 Flight 501: The 1996 first flight of the Ariane 5 rocket, which ended in destruction shortly after launch. A reused conversion routine caused an overflow that helped destroy the rocket.
Software vulnerability: A weakness in software that an attacker can exploit to compromise confidentiality, integrity, or availability. A vulnerability is a security-relevant weakness; many bugs have no exploitable security impact.
Software failure: An observable inability of a system to perform a required function within specified limits. A bug becomes a failure when execution produces unacceptable behavior.
Bug tracking system: Software for recording, prioritizing, assigning, and tracking defects and other work items. Teams use issue records to coordinate investigation and resolution.
Therac-25: A radiation therapy machine associated with software-related accidents in the 1980s. Its software and safety design failures led to dangerous radiation overdoses.
Technical debt: Future development cost created by expedient design or implementation choices. Technical debt can make bugs harder to prevent and fix, but is not itself necessarily a bug.
Race condition: A flaw in which behavior depends on the timing or ordering of concurrent operations. Timing-dependent bugs often appear only under particular execution schedules.
Regression testing: Testing that checks whether changes have broken previously working behavior. A fix can introduce new bugs or restore an old one; regression tests guard against both.

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VulnerabilityRelated: A bug becomes a vulnerability when it enables a security violation.