known quantity
C1-C2 / Upper Intermediate to AdvancedPrimarily formal; used in academic, business, and political discourse. Less common in casual conversation.
Definition
Meaning
A person or thing whose characteristics, abilities, or behavior are already understood and predictable.
In extended use, can refer to a concept, situation, or entity whose properties are familiar and whose outcomes are not surprising or risky. In business/scientific contexts, often contrasted with 'unknown quantity' or variables needing investigation.
Linguistics
Semantic Notes
Always used as a noun phrase. The figurative use is far more common than the literal mathematical/scientific sense. Implicitly carries connotations of reliability, predictability, and (often) low risk. Can be used positively (a safe, dependable choice) or negatively (someone predictable, lacking potential for surprise or growth).
Dialectal Variation
British vs American Usage
Differences
The term is identical in meaning and structure in both dialects. No spelling, grammatical, or direct lexical differences.
Connotations
In both dialects, carries similar connotations. Slightly more prevalent in British political journalism and American business/HR contexts.
Frequency
Moderately low frequency in both, with a slight edge in usage in American English due to corporate jargon.
Vocabulary
Collocations
Grammar
Valency Patterns
[Subject] be a known quantity to [Person/Group]treat/consider/view [Object] as a known quantityVocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “A known quantity is better than an unknown variable.”
Usage
Context Usage
Business
Refers to an employee, partner, or market with a track record, used in risk assessment and hiring/promotion decisions. 'We promoted her internally because she's a known quantity.'
Academic
Used in research design and scientific writing to describe a controlled or previously studied variable. 'The placebo was the known quantity in the clinical trial.'
Everyday
Used to describe a person whose behavior is very predictable. 'I'll ask Tom to help; he's a known quantity and won't let us down.'
Technical
In mathematics and science, refers to a variable with a fixed or determinable value, as opposed to an 'unknown'. Used in equations and problem-solving contexts.
Examples
By Part of Speech
verb
British English
- This variable is known to affect the outcome.
- The formula requires quantities known to three decimal places.
American English
- We have known for years that this method works.
- The quantities known at the start were insufficient.
adverb
British English
- He is known to frequent that café.
- The drug is known internationally for its side effects.
American English
- She is known for her charitable work.
- The brand is known worldwide.
adjective
British English
- He is a well-known author.
- There is no known cure for the condition.
American English
- She is a known expert in the field.
- It's a little-known fact about the company.
Examples
By CEFR Level
- The number five is a known quantity.
- My teacher is a known quantity; she is always kind.
- In the experiment, water temperature was the known quantity.
- I trust my brother to help because he is a known quantity.
- The board favoured the internal candidate as he was a known quantity with a proven track record.
- The stability of the Swiss franc makes it a known quantity for international investors.
- While the new policy carries risks, the economic impact of the current regime is at least a known quantity.
- Her voting record in parliament made her a known quantity to party strategists, which ultimately limited her appeal as a reformer.
Learning
Memory Aids
Mnemonic
Think of a 'quantity' in a maths equation that you already 'know' the value of. You don't need to solve for it—it's predictable and certain. Apply this to people or situations.
Conceptual Metaphor
PEOPLE/THINGS ARE MATHEMATICAL VARIABLES (A person's predictability is conceptualized as a variable with a known, fixed value.)
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid literal translation (*известное количество).
- The English idiom refers to *predictability, not just fame. A *известная величина is a good conceptual equivalent.
- Do not confuse with 'well-known figure' which emphasizes fame, not predictability.
Common Mistakes
- Using it as an adjective: 'He is very known quantity.' (Incorrect) vs. 'He is a known quantity.' (Correct).
- Confusing with 'quantity known' which is a literal mathematical description, not a fixed idiom.
Practice
Quiz
In which context is 'known quantity' LEAST likely to be used appropriately?
FAQ
Frequently Asked Questions
Yes, it often implies reliability and low risk, which is positive in contexts like hiring or investing. However, it can also imply a lack of novelty or excitement.
It is a two-word noun phrase and is not hyphenated when used as such (e.g., 'a known quantity'). Hyphens may appear if it functions as a compound modifier before a noun (e.g., 'a known-quantity approach'), but this is rare.
The direct opposite is 'unknown quantity,' meaning a person or thing whose nature or effect is unpredictable or not yet understood.
It can refer to any entity—people, objects, concepts, organizations, or market forces—whose properties and behavior are familiar and predictable.