Glossary
Mootness
When events have made a case no longer relevant: there's nothing for the court to decide because the dispute has resolved itself. A moot case is generally dismissed, since federal courts decide actual disputes, not academic questions.
If a plaintiff sues to stop something and the defendant stops doing it before the case is decided, the case might be moot. If a plaintiff sues over a job application denial and then gets the job, the original lawsuit might be moot.
There are exceptions. A case isn't moot if the defendant is likely to repeat the conduct. Class actions sometimes survive even if the named plaintiff's claim becomes moot. And some questions are "capable of repetition yet evading review" (election disputes, short-term injunctions) and courts will hear them despite mootness.