by-elections

Its a special kind of elections, held to fill office that has become vacant between regularly scheduled elections
 . Usually this occurs when the incumbent has died or resigned, but it may also occur when the incumbent becomes ineligible to continue in office, for example because of a recall, ennoblement (colloquially known in the United Kingdom as being "kicked upstairs") or a sufficiently serious criminal conviction. By-elections have also been called as a result of a constituency election being invalidated due to voting irregularities regulary scheduled