Why 'referendums' is arguably more correct than 'referenda' as a plural
Referendum is a Latin gerundive from referre, to carry back, as in a proposal that must be carried back to the people. Grammatically, the Latin plural referenda would mean several matters to be referred, so referendums is the more logical plural for several ballots on one issue. Agenda and memorandum share the same construction.
The gerundive carries a sense of obligation: agenda are things that must be driven forward, memorandum a matter that must be remembered, corrigenda things that must be corrected. Both the name and the practice probably arose in Graubünden, a Swiss canton, perhaps by the sixteenth century. Plebiscite has a different pedigree, from the plebiscita, decrees of the Plebeian Council of the Roman Republic.
Countries do not always use the two words consistently. Australians often claim a referendum changes the federal constitution while a plebiscite does not, but the 1916 vote on conscription was a federal referendum on a non-constitutional question, and Western Australia's 2009 poll on daylight saving was also called a referendum. In Ireland, adopting the constitution was a plebiscite, while later amendments are referendums.
Such votes may be binding or merely advisory, the latter working like a very large opinion poll. David Altman sorts them along several lines: mandatory or optional, started by citizens or by authorities, and proactive, proposing a change, or reactive, blocking one. Mandatory referendums require no petition. Australia, Ireland, Switzerland, Denmark and 49 of the 50 American states put constitutional amendments to a compulsory vote, Delaware being the lone exception. California cannot borrow more than $300,000 without a statewide bond vote.
Switzerland requires a referendum before joining a supranational community or a collective security treaty, but that rule has been triggered only once, in a failed 1986 attempt to join the United Nations. After a dip in the mid-twentieth century, referendums have grown steadily more popular since the 1970s, a trend attributed to voters caring more about specific issues than about party loyalty.
Source: Referendum
