What do we call the election that is held to replace a Member of Parliament (MP) when they die or resign?

Okay, so when a Member of Parliament, or MP, leaves their position before the end of their term, whether it's because they've sadly passed away or decided to resign, a special election needs to be held to fill that vacant seat. This isn't a regular general election, which happens every few years for all the seats in Parliament. Instead, it's a specific election just for that one constituency that's now without representation. This is called a "by-election." Think of it as a way to "bye-pass" the usual election schedule because someone has left early. The term has been used since the 19th century, and it's a crucial part of ensuring that every area of the UK has someone representing them in Parliament. While "re-selection" or "selection" might sound plausible, they usually refer to processes within a political party, not the actual public vote to choose a new MP. "Hustings" are meetings where candidates present their views, but it's not the election itself.