A referendum is a direct vote by citizens (rather than their representatives) on a proposed law or political issue. It can be binding (resulting in a new policy) or non-binding and functions like a large opinion poll. The term is derived from the Latin words refer, meaning to send on and plebiscite, meaning a ballot. There are many different types of referendums, as each country, state or organization has its own statutes and rules about holding these votes. But there are a few key design features that help to define a referendum.

One is whether a referendum is mandatory under a country’s constitution or laws; and the other is whether it has been initiated by the government or legislature or citizens. Mandatory referendums tend to be held over very serious issues, while optional referendums are usually held over a broad range of topics. Whether the referendum is binding or not and whether it requires a minimum participation quorum are other features that help to differentiate a referendum from an ordinary election.

The core purpose of a referendum is to engage national publics in political debate and decision-making, which are often passive or actively excluded from the business of politics. However, referendum campaigns can often be socially divisive and savagely aggressive. In addition, the low participation quorums that are sometimes required to pass a referendum can undermine democracy by invalidating results if there is insufficient support for a change. In light of these perils, the question of when to hold a referendum can be a profoundly difficult one for governments.