From The Economist:
For more than a millennium after the fall of Rome, educated Europeans were distinguished by their knowledge of Latin. One of the three subjects of the trivium—the basic tier of a classical education, itself based on a Roman model—was Latin grammar. Europeans have long since stopped writing primarily in Latin, but learned people are still expected to be able to deduce that to “decimate” means to destroy a tenth of something (a mutinous legion was punished in this way), or sprinkle annus mirabilis and mutatis mutandis into their speech.
It is not for lack of knowledge of, or affection for, Latin that The Economist marks a change this week. The reform involves one of the most curiously polarising issues an ending on a foreign word has ever generated in English. We will now allow singular use of data alongside the plural. Specifically, when considered as a concept—as in data is the new oil—the singular will be acceptable, as well as when the data in question is considered as a mass (the data on this mobile-phone plan is insufficient). However, when data points are considered as a group of pieces of information, the plural should still be used: data from the National Oceanic and Atmospheric Administration indicate the hottest summer of all time.
Data, as every child at a grammar school once knew, is the plural of Latin’s datum, “something given”. Originally that plural sense was carried over into English. But already in 1702, the Oxford English Dictionary records, came the first appearance of singular data, in an astronomy textbook. This was almost 60 years after plural data was first recorded.
The rise of computing has changed the balance. While an 18th-century scholar’s data might be a single column of numbers, today’s computers quickly manage billions of bytes. Data points begin to seem like the water molecules in the ocean and so, in such contexts, to be perceived as a mass. Singular data is now more common than the plural in books, and far more prevalent on the web.
Data is hardly the first foreign word to undergo grammatical change in English. The nearest equivalent is agenda, an old plural of agendum, “something to be acted on”. Once those collected agenda started being thought of as a list, the English singular was born. (Candelabra, stamina and insignia were all Latin plurals, too.) The Economist’s style guide prescribes a list of Latin -um words in English that pluralise with -a (memoranda, strata), but many more that violate Latin grammar and take -ums (forums, stadiums, ultimatums). It demonstrates that those words are now English; Latin rules need not apply.
Those who oppose singular data argue that the word refers to a set of numbers. Yet the properties of the thing itself are not a reliable guide to a term’s grammar. Go to a shop where dried goods are sold from barrels and note rice (a singular) next to lentils (a plural), and wheat (singular) next to oats (plural). Head to the pasta section and see what happens to other languages’ words in English: spaghetti and lasagne, both Italian plurals, are singular when served up in English.
Link to the rest at The Economist