Plural of Datum
“Datum” is a specialized singular noun meaning one item or piece of data, and its traditional plural is “data.” Modern usage has also developed “data” as a mass/uncount noun, so agreement with “data” varies by context and editorial convention.
The traditional plural of “datum” is “data.” In modern English, however, “data” is also widely treated as an uncount noun that can take singular agreement, especially outside highly formal or technical contexts.
Key details
Further guidance
Core difference
The inflection is “datum” → “data,” but modern “data” can also function as an uncount noun.
Fast Test
Use “datum” when you genuinely mean one discrete item in a context that uses the term. For multiple items, “data” is the traditional plural; follow the governing style or field for singular versus plural agreement with “data.”
Usage Boundary
Do not force “datum” into ordinary prose merely to create a singular for “data.” The singular survives mainly in specialized contexts, while mass-noun “data” is established in modern usage.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Datum — Cambridge Dictionary (opens in a new tab)Cambridge University Press · Direct lexical evidence that datum is a specialized singular noun whose plural is data.
- Data — Cambridge Dictionary (opens in a new tab)Cambridge University Press · Direct usage evidence that data historically functions as the plural of datum and is also widely used as an uncount noun with singular agreement.