Difference between Bug, Defect and Error

Bug, defect, and error are terms that are commonly used in software development, but they have slightly different meanings:

Bug:

A bug is a coding error or mistake in software that causes it to behave unexpectedly or not according to its specifications. Bugs can be introduced at any stage of software development, including design, coding, and testing.

Defect:
A Defect is a deviation from the requirements or specifications of a software product. It can be caused by a bug, a design flaw, or a misinterpretation of the requirements. A defect is essentially a problem with the software that prevents it from working as intended.

Categories of defects - There are three main category of defects;
Wrong: The requirements have been implement the wrong way. This defect is a variance from the given specification.

Missing: There was a requirement given by the client and it was not done. This is a variance from the specifications, an indication that a specification was not implemented, or a requirement of the customer was not noted correctly.

  Extra: A requirement incorporated into the product that was not given by the end   customer. This is always a variance from the specification, but may be an attribute  desired by the user of the product. However, it is considered a defect because it’s  a variance from the existing requirements.

  Error: An error is a human mistake that results in a problem with the software. Errors can occur at any stage of software development, including requirements gathering, design, coding, and testing. An error can cause a bug or a defect.

Fault: A wrong or mistaken step, process or Data definition in a computed program which causes the program to perform in an unintended or unanticipated manner.

In summary, bugs and defects are related to the actual software code, while errors are related to human actions or decisions. Bugs and defects are often used interchangeably, but they have slightly different meanings.