In English a common noun can be used as an adjective, the linguistic term is called a noun adjunct, or an attributive noun. Example: car driver, star size, chodolate flavor, impact prediction.

Can a proper noun be used as an adjective too? EG: David method, Peter weight, Beethoven Park, Paganini Notation, Born equation, Lincoln football team captain.

(I mean without the 's)

Probably yes, e.g. the Born equation, but there is Ohm's law.. not Ohm law in physics. Can it be distinguished when yes and when no? Is one of the versions more formal?

Thank you.

  • No; the linguistic term is modifier. But in examples like your "car driver", "car" is not a modifier but a complement. (Note that in modern grammar the term 'adjunct' refers to modifiers in clause structure, not in phrase structure.)
    – BillJ
    Mar 22, 2023 at 14:16
  • Yes: proper nouns can be modifiers, as in "Egyptian cotton shirt".
    – BillJ
    Mar 22, 2023 at 14:19

4 Answers 4


Looking for examples of eponyms, I found this in the Wikipedia article:

English can use either genitive case or attributive position to indicate the adjectival nature of the eponymous part of the term. (In other words, that part may be either possessive or non-possessive.) Thus Parkinson's disease and Parkinson disease are both acceptable. Medical dictionaries have been shifting toward nonpossessive styling in recent decades.[26] Thus Parkinson disease is more likely to be used in the latest medical literature (especially in postprints) than Parkinson's disease.

The possessive form is traditionally used for scientific laws, as in 'Ohm's Law'.

So, yes, both forms can be used and there isn't a difference in the level of formality.


It seems to me that proper nouns (without using the Saxon genitive or actively changing them into an adjective, as in the change from 'Shakespeare' to 'Shakespearean') can be used as an adjective, often (but not always - think of 'a Beckett play') as a component of another proper name.

There are many such examples.

Place names (off the top of my head, from my hometown):

  • Nassau Street
  • FitzWilliam Square
  • Waltham Terrace

... but

  • George's Street (for example)

Scientific theories, principles, equations, etc.:

  • The Peter Principle
  • The Schrödinger Equation
  • The Biot–Savart Law

... but

  • Darwin's Law
  • Snell's law
  • Pythagoras' Theorem ...

(see https://en.wikipedia.org/wiki/List_of_scientific_laws_named_after_people)


  • A New York state of mind
  • A London stockbroker
  • A Manchester street
  • A Rousseau quote
  • An Eccles cake


We can see from the above examples that scientific laws, principles, equations, etc. that use an unaltered name as an adjective tend to take the definite article as part of the name. Such place names don't.

I can find no rule as to when you should use a Saxon genitive and when you simply use the proper name as if it were an adjective.

There seem to be more street names without the Saxon genitive than with it, but I can't identify any rule that governs which pattern to use, except possibly how pleasing the resulting expression is to the ear.

With scientific names the opposite seems to be the case; i.e. there are more names with Saxon genitives than without them, but I can see no rule there either, except that such expressions involving two or more hyphenated scientists never use a Saxon genitive form.

It's also worth taking a look at the separate but related subject of 'proper adjectives', which are adjectives rooted in proper nouns, usually converted by changing the word ending.

(see https://www.englishclub.com/grammar/adjectives-proper.php)

  • The term is 'modifier of', not "as an adjective"
    – BillJ
    Mar 22, 2023 at 14:21
  • 1
    Different grammaticians have different nomenclatures.
    – Jaime
    Mar 22, 2023 at 14:23
  • The term adjective doesn't come into it. The tradition is to call things "adjectives" whenever their intuitive (semantic) function is to modify the meaning of a noun or add information about the referent of a noun. This gives no real concept of adjective at all. It becomes the largest category of all, because every noun must be in it as well as every real adjective and every past participle form of a verb and every gerund-participle of a verb and every other item that can ever modify a noun. They even call relative clauses 'adjective clauses'. It's madness! See what I mean?
    – BillJ
    Mar 22, 2023 at 14:36
  • You seem to be arguing against yourself now, at least in places. Though I'm not at all sure what you're referring to as "madness."
    – Jaime
    Mar 22, 2023 at 14:45
  • 1
    @BillJ: I think we'll leave it at that, Bill.
    – Jaime
    Mar 22, 2023 at 14:51

I would say that there is really no alternative to learning and remembering the different, and inconsistent usages. There may be regional differences. One I am thinking about is using the name of a syndrome's or disease's discoverer to name the condition. In British English, they seem to mainly use the surname in possessive form, and in American, often, but not always, just the name. The British 'Down's Syndrome' is usually 'Down Syndrome' in America. But the American 'Lou Gehrig's disease' is the British 'motor neurone disease' (Many Brits, apart from people with some interest in the disease, have never heard of Lou Gehrig).

In 1975 the United States National Institutes of Health conference on nomenclature of malformations recommended eliminating the possessive form, on the grounds that 'the author neither had nor owned the disorder'. Many linguists find this a startling reason.

The 'rule' that the NIH invented is not applied consistently: Parkinson's disease, Alzheimer's disease, Behcet's syndrome, Hodgkin's disease, but also Sanjad-Sakarati syndrome, Hutchinson-Guildford disease, Edwards syndrome (one can imagine an apostrophe after the 's'!) Ehler Danlos syndrome, Lambert-Eaton syndrome.

Interesting discussion here:

Down vs Down's (Huffington Post)


The examples you cite, such as 'Ohm's Law' or 'The David Method', would be compound nouns. Adjectives commonly form part of compound nouns (eg "a wet suit") but as a whole, it is still a noun, so there isn't really any argument for saying that 'Ohm' or 'David' are being used as adjectives - especially when they are expressed as possessive nouns. Examples such as 'Ohm's Law' are also proper nouns in their own right, so there really shouldn't be any debate over how to express it any more than people should debate on how to spell your name - just check a scholarly resource.

A few well-known proper nouns are used as common nouns - for example, you might call someone a Judas or a Karen, and while these may arguably describe a person they are still not being used as adjectives because they are saying what a person is rather than what they are like.

In all cases that I can think of where something is described by reference to a proper noun, it usually takes on some other form - for example 'Orwellian', or 'Dali-esque'.

In short, we don't really use proper nouns directly as adjectives - it would be too confusing. For example, if you said "this painting is Da Vinci" it would be taken to mean that Da Vinci himself painted it. Saying it is "Da Vinci-esque" or "Da Vinci-like" makes it clear you are just making a comparison, describing its qualities as being like Da Vinci's own work.

  • Didn't Dan Brown perpetrate a piece of written work that used 'Da Vinci' that way? And mis-spell 'da Vinci' into the bargain? Like you did? ;-) Mar 22, 2023 at 9:32
  • Interesting when multiple authors are involved. I can find a square root by using Newton's method, or a later development, the Newton-Raphson method. I have been amused to see the latter (e.g. on web sites) called called 'Newton-Raphson's method'. Confusion abounds. Mar 22, 2023 at 9:44
  • @MichaelHarvey The 'Da Vinci Code' was a code attributed directly to Da Vinci. It wasn't a code in the style of Da Vinci. And further, 'The Da Vinci Code' (with a definite article) is a compound noun. So it proves all of my points.
    – Astralbee
    Mar 22, 2023 at 10:17
  • @MichaelHarvey If by 'misspelling' you mean writing 'Da Vinci' with a capital letter... that is the common way to write the surname in isolation. 'Leonardo da Vinci' was a member of the Da Vinci family.
    – Astralbee
    Mar 22, 2023 at 10:49
  • 1
    No: "Shakespeare is not an adjective but a proper name used as a modifier. And "David method" is not a compound noun but a syntactic construction consisting of modifier +head noun. Note that compound words are written as either a single word or sometimes hyphenated, but not as separate words.
    – BillJ
    Mar 24, 2023 at 9:21

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