Chapter 1 – Fundamentals of Testing
Defect – ISTQB Definition
Last Updated: July 12, 2026 · SoftwareTestPilot QA Team
Official ISTQB Definition
An imperfection or deficiency in a work product where it does not meet its requirements or specifications.
In simple words
A flaw in the product — code, requirement, or design — that could cause a failure when executed.
Exam tip
Know the chain: a person makes an error → introduces a defect → which, when executed, may cause a failure.
Related terms
- FailureThe visible symptom — the app crashed, the calculation was wrong, the button did nothing.
- SeverityHow bad the bug is technically — does it crash the app, corrupt data, or just misalign a label?
- Regression TestingAfter any change — bug fix, new feature, config update — you re-run existing tests to make sure nothing that used to work has broken.
Practice this term in the ISTQB Mock Test
40 CTFL v4.0 questions, 60-minute timer, instant scoring and chapter-wise breakdown.
Practice in Mock Test