Severity
// Definition
A rating of how badly a defect affects the system or users, independent of when it should be fixed. Common levels: critical (system unusable or data loss), major (core feature broken with no workaround), minor (non-critical degradation), trivial (cosmetic only). Severity measures impact; priority measures urgency — a cosmetic bug on the login page might be low severity but high priority for a public launch.
// Related terms
Bug Lifecycle
The stages a defect passes through from discovery to closure: New → Assigned → In Progress → Fixed → Verified → Closed (with possible Reopened, Deferred, or Rejected branches).
Defect Density
Defects per unit of size — typically per thousand lines of code or per function point. Useful for spotting unusually buggy modules and tracking quality trends over time, with the usual caveats about goal-induced metric gaming.
Defect Leakage
The ratio of defects found in production to total defects (production + pre-release). Measures how well testing caught bugs before users did. Lower is better.