an unknown quantity

USAGE SUMMARY

"an unknown quantity" is correct and usable in written English.
You can use it when you do not know how much of something there is or is available, or when something is uncertain. For example, "The future is an unknown quantity; no one can really predict what will happen."

✓ Grammatically correct

News & Media

Formal & Business

Science

Human-verified examples from authoritative sources

Exact Expressions

56 human-written examples

An improvisatory performance is, by its nature, an unknown quantity.

The New Yorker

Spin is an unknown quantity.

The Guardian - Sport

I am an unknown quantity".

The New York Times - Sports

Buscombe remains an unknown quantity.

The Guardian

Mr Obama is an unknown quantity.

The Economist

AIDS is still an unknown quantity.

The Economist

But Danish television was an unknown quantity.

The New Yorker

He is something of an unknown quantity.

The New York Times - Arts

My gene pool was an unknown quantity.

The Guardian - Books

Maradona working alone is an unknown quantity.

The Guardian - Sport

He is still an unknown quantity in his homeland.

The Guardian - Sport

Expert writing Tips

Best practice

Apply the phrase to situations or emerging technologies where the eventual outcome or impact is difficult to forecast due to a lack of data.

Common error

While "an unknown quantity" is the standard idiom for someone whose impact is unpredictable, avoid using it when you strictly mean they have unknown traits or characteristics. In those cases, "an unknown quality" might be literal but less idiomatic. Remember that quantity here refers to the mathematical 'unknown' (like x), not physical volume.

Linguistic Context

This phrase serves as a noun phrase functioning as a predicative nominative or a direct object. According to Ludwig, it is primarily used to identify a subject that lacks a track record or predictable behavior. It follows standard English grammar rules and is categorized as Correct by Ludwig AI.

Expression frequency: Very common

Frequent in

News & Media

65%

Formal & Business

20%

Sports

10%

Less common in

Science

3%

Academic

1%

Social Media

1%

Ludwig's WRAP-UP

In conclusion, "an unknown quantity" is a highly effective and widely used idiom that transitions seamlessly from its mathematical roots into everyday professional English. Ludwig AI confirms its status as a correct and very common expression, especially within elite journalistic circles. Whether you are describing a new political candidate, a volatile market or an unproven athlete, this phrase conveys a specific type of uncertainty: one where the subject is present but their potential magnitude is yet to be revealed. Use it to add a layer of analytical sophistication to your writing when dealing with the unpredictable.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

an unknown factor

Focuses more on the element as part of a larger equation or problem

a wild card

More idiomatic and emphasizes total unpredictability

an unproven entity

Highlights a lack of a recorded track record or history

an uncertain variable

More scientific or mathematical in tone

a dark horse

Specifically refers to an unknown competitor who might win

an enigma

Suggests something mysterious or difficult to understand

an anonymous element

Emphasizes the lack of identifying information

a mystery

More general and less focused on measurable impact

an unpredictable force

Emphasizes the potential for active change or disruption

an X factor

Refers to a specific but hidden quality that could determine success

FAQs

How do I use "an unknown quantity" in a sentence?

You can use it to describe a person or thing that is unpredictable, such as: "The new CEO is still something of "an unknown quantity" in the tech world".

What is a synonym for "an unknown quantity"?

Depending on the context, you can use phrases like "a wild card", "an unknown factor" or "an unproven entity".

Is "an unknown quantity" formal?

Yes, it is considered neutral to formal. It appears frequently in prestigious news outlets like The New York Times and The Economist, making it suitable for professional writing.

What is the origin of the phrase "an unknown quantity"?

It originates from mathematics, specifically algebra, where it refers to a variable (like x) whose value is not yet determined. In general English, it has evolved to mean a person or thing whose influence cannot yet be predicted.