A bug is an error/mistake in the software that produces an incorrect or unexpected result or behavior.
This tag will be added to questions about problems that have subsequently been confirmed to be caused by bugs in Mathematica. It should be accompanied by the appropriate version tag. It should not be used when asking new questions. If you know that a certain behavior is a confirmed bug, then please report it to Wolfram Support instead (or e-mail firstname.lastname@example.org).