Datum Plural Form: Rule, Examples, and Mistakes
The plural of datum is data. This is a Latin plural that follows the rule for second-declension neuter nouns: the singular ends in -um, and the plural ends in -a. So datum becomes data. However, in modern English, data is often treated as a singular mass noun (e.g., “the data is clear”), which creates confusion. This guide explains the original rule, the shift in usage, and how to choose the correct form in different contexts.
Quick Answer
Singular: datum (one piece of information)
Plural: data (multiple pieces of information)
Formal/technical use: Keep the distinction — “these data show” (plural).
Informal/general use: “Data” as a singular mass noun is widely accepted — “the data is ready.”
Understanding the Rule
The word datum comes directly from Latin, where it is the neuter singular form of the past participle of dare (to give). It literally means “something given.” In Latin grammar, neuter nouns ending in -um form their plural by changing the ending to -a. This is the same pattern you see in other Latin loanwords:
- memorandum → memoranda
- curriculum → curricula
- medium → media
- bacterium → bacteria
So the strict, traditional plural of datum is data. If you are writing for a scientific journal, a medical report, or any formal academic context, you should maintain this distinction.
Formal vs. Informal Usage
English has gradually changed how data is used. Here is the key difference:
| Context | Preferred Form | Example |
|---|---|---|
| Formal scientific writing | data as plural (datum singular) | “These data were collected over three years.” |
| Medical research papers | data as plural | “The data indicate a significant improvement.” |
| Business reports (formal) | data as plural | “The data support our conclusion.” |
| Everyday conversation | data as singular (mass noun) | “The data is stored on the server.” |
| Email to a colleague (informal) | data as singular | “Let me know when the data is ready.” |
| General blog writing | data as singular | “This data shows a clear trend.” |
Important nuance: Using data as a singular noun is no longer considered incorrect in most contexts. However, some readers (especially in academic or medical fields) still expect the plural form. When in doubt, match your audience. If you are writing a patient report, use data as plural. If you are writing an internal email, singular is fine.
Natural Examples
Here are examples that show how datum and data appear in real writing and speech.
Formal / Academic
- “Each datum was verified by a second technician.” (singular, formal)
- “These data suggest a correlation between dosage and recovery time.” (plural, formal)
- “The data are consistent with previous findings.” (plural, formal)
Informal / Everyday
- “I need that data by Friday.” (singular, informal)
- “The data is corrupted — can you re-upload it?” (singular, informal)
- “We don’t have enough data to make a decision.” (singular, informal)
Medical Context
- “The patient’s datum for blood pressure was recorded at 8:00 AM.” (singular, one reading)
- “All data from the clinical trial have been reviewed.” (plural, formal)
- “The lab data shows normal kidney function.” (singular, informal report)
Email Examples
- Formal email: “Please find attached the data that were requested during the audit.”
- Informal email: “The data you sent looks good. I’ll review it this afternoon.”
Common Mistakes
Even native speakers make errors with datum and data. Here are the most frequent ones:
Mistake 1: Using “datums” as the plural
Some people assume datum follows regular English rules and write datums. This is incorrect in standard English. The plural is data.
Wrong: “We collected three datums from each patient.”
Right: “We collected three data points from each patient.” (or “three data”)
Mistake 2: Mixing singular and plural in the same sentence
If you treat data as plural, keep the verb and pronouns plural throughout.
Wrong: “The data is clear, and they support the hypothesis.” (mixes singular verb with plural pronoun)
Right: “The data are clear, and they support the hypothesis.” (all plural)
Mistake 3: Overcorrecting to “datum” in all singular contexts
In everyday speech, using datum sounds overly formal and can confuse listeners. Use datum only when you need to emphasize a single piece of information.
Awkward: “Can you check that datum before the meeting?”
Natural: “Can you check that data point before the meeting?”
Mistake 4: Forgetting the Latin plural in formal writing
In a research paper, writing “the data shows” (singular) may be flagged by a reviewer. Stick with “the data show” (plural) in formal contexts.
Better Alternatives
If you are unsure whether to use datum or data, or if you want to avoid the confusion entirely, here are some alternatives:
- For a single piece of information: Use “data point,” “observation,” “measurement,” or “value.”
- For multiple pieces: Use “dataset,” “results,” “findings,” or “information.”
- In informal writing: Use “data” as a singular mass noun (e.g., “the data is ready”).
When to use “datum”: Use it in formal, technical, or scientific writing when you need to refer to one specific unit of data. For example, in a medical chart: “The datum for systolic pressure was 120 mmHg.”
When to use “data” as plural: Use it in academic papers, research reports, and any context where precision is expected and your audience is familiar with the Latin plural.
When to use “data” as singular: Use it in emails, conversations, blog posts, and general business writing. This is the most natural choice for most modern English speakers.
Mini Practice
Test your understanding with these four questions. Choose the correct form for each sentence.
1. The researcher recorded each _____ carefully before entering it into the system.
a) datum
b) data
c) datums
Answer: a) datum (singular, one item)
2. The _____ from the experiment were analyzed using a statistical model.
a) datum
b) data
c) datums
Answer: b) data (plural, formal context)
3. In the email to the team, she wrote: “The _____ you requested is attached.”
a) datum
b) data
c) datums
Answer: b) data (singular mass noun, informal email)
4. Which sentence is correct for a medical journal?
a) This data shows a significant effect.
b) These data show a significant effect.
c) These datums show a significant effect.
Answer: b) These data show a significant effect. (plural verb and pronoun for formal writing)
Frequently Asked Questions
Is “data” singular or plural?
Technically, data is the plural of datum. However, in modern English, data is commonly used as a singular mass noun (like “information”). Both uses are correct, but the choice depends on your audience and context. In formal writing, treat data as plural. In everyday use, singular is fine.
Can I use “datas” as the plural of “data”?
No. Datas is not a standard English word. The plural of data is still data (or you can use data sets or datasets if you need to emphasize multiple collections).
When should I use “datum” instead of “data”?
Use datum when you are referring to a single, specific piece of information, especially in technical or scientific writing. For example, “Each datum was verified” means each individual measurement was checked. In most other situations, data (as singular or plural) is more natural.
Is it wrong to say “the data is”?
No, it is not wrong. Many style guides, including the Associated Press Stylebook, now accept data as a singular noun. However, some academic and scientific style guides still prefer the plural. If you are writing for a publication, check their style guide. Otherwise, use what feels natural for your audience.
For more help with plural forms, visit our Plural Spelling Rules section or explore Confusing Plurals for similar words like criterion/criteria and phenomenon/phenomena. If you have questions about other medical terms, check our FAQ page.
