What is the term for an election held to fill a parliamentary seat when an MP resigns or dies?

Okay, so when a Member of Parliament, or MP, leaves their position before the end of their term, whether it's because they've resigned, sadly passed away, or sometimes even taken on a role that disqualifies them from being an MP, we need a way to fill that empty seat in the House of Commons. That's where a by-election comes in. Think of it as a special, localized election just for that specific constituency. It's important to remember that general elections happen at fixed intervals, usually every five years, and involve the entire country voting for all MPs. But a by-election is triggered by an unexpected vacancy. The term "by-election" is used because it's an election held *by* the way, or *in addition to*, the regularly scheduled general elections. It's a mini-election, if you will, to ensure that every area of the UK is properly represented in Parliament. So, while "re-election" might sound plausible, it only applies when an MP's term is finished and they're seeking to be elected again in a general election.