What is the difference between a bug and a defect?

Error — a human action (developer, tester, analyst) that leads to an incorrect result or state. This can be a typo in the code, a misunderstanding of requirements, or incorrect test execution.

Defect — the manifestation of this error in the product. It is a discrepancy between how the system actually works and how it should work according to the requirements. That is, a defect is a discovered bug in the software. A defect can be found at early stages of development (for example, in the code) or at later stages (during testing or user operation).

Thus, an error is the cause, and a defect is the consequence.