“Data” Is Whichever You Decide, As Long As You Decide

The data is clear or the data are clear?

Both. This is a case where the honest answer really is it depends, and knowing what it depends on is the useful part.

Where it comes from

Data is the plural of the Latin datum, meaning a thing given. Strictly, one datum, several data.

But datum has almost vanished from English. Nobody says this datum suggests. When a plural loses its singular, it tends to get reinterpreted as a mass noun — something you measure rather than count, like water, information or evidence. Mass nouns take singular verbs.

That is the whole mechanism, and English has done it before: agenda was a Latin plural and is now firmly singular, with a new plural agendas.

What the style guides say

• Chicago accepts singular in general writing, plural in scientific contexts.
• AP uses singular for a collection, plural for individual items.
• Merriam-Webster records both as standard.
• Nature and most scientific journals require the plural.
• The Economist uses the plural. Most newspapers use the singular.

No consensus, and no authority claiming the other side is wrong.

The rule that actually works

Ask what you mean.

• A single body of information → singular. The data is stored on three servers. You are not thinking of individual readings.
• Individual measurements you could count → plural. The data were collected on separate days and analysed independently.

This is the same distinction English already makes elsewhere. The team is winning treats the team as one thing; the team are arguing among themselves treats it as individuals. Nobody finds that troubling.

Know your room

Register decides more of this than logic does.

In a scientific paper, in a statistics department, or in a journal that requires it, use the plural. It signals that you know the convention, and getting it wrong there is genuinely marked.

In business writing, journalism, technical documentation and general prose, the singular is now normal and the plural can read as fussy.

The other Latin plurals

The same drift is at various stages elsewhere:

• Media — plural of medium. Now usually singular for the press: the media is.
• Criteria — plural of criterion. Still firmly plural. A criteria is an error most readers notice.
• Phenomena — plural of phenomenon. Still plural.
• Bacteria — plural of bacterium. Still plural in scientific writing, drifting elsewhere.
• Agenda — fully naturalised as singular.

The pattern: the further a word travels from technical use, the faster the singular wins.

The only real error

Inconsistency. The data is compelling. They were gathered over two years. Whichever you choose, hold it for the whole document. That is the one thing every editor will actually mark.

Checked against Merriam-Webster, the Chicago Manual of Style and the AP Stylebook. Spotted an error? Tell us — see our editorial policy.