From the Oxford English Dictionary at OED:

proof of concept n. evidence (usually deriving from an experiment or pilot project) demonstrating that a design concept, business idea, etc., is feasible; a piece of such evidence; freq. attrib.

1994 San Antonio Business Jrnl. (Nexis) 19 Aug. a4 "We built this center as a proof of concept."

2001 Today's Pilot Feb. 51/1 "Although the GA-200 is a totally new aircraft, some heavily modified Pawnees were used as proof-of-concept aircraft."

So is it both a noun and an adjective?

I wrote in a document "(...) successfully evaluated through a proof of concept prototype." and now I'm wondering whether I should change it into "(...) successfully evaluated through a proof of concept.". I left the dashes out in both cases.

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    Normally there will be dashes when used attributively (≈ as an adjective) and no dashes when used as a noun phrase. Your suggested change makes no sense, though: how do you evaluate something through a piece of evidence? You can, I suppose, evaluate something through a prototype in the right context, but not through proof. – Janus Bahs Jacquet Aug 27 '13 at 13:01
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    If it is hardware, I would think successfully evaluated through a prototype we buildt as a proof of concept. – mplungjan Aug 27 '13 at 13:02
  • @mplungjan It's software. Following your suggestion, I changed it to "A proof-of-concept prototype is implemented and successfully evaluated.". – Daniel Aug 27 '13 at 13:13
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    In that sentence you can skip the prototype - A proof-of-concept has been implemented and successfully evaluated with or without dashes – mplungjan Aug 27 '13 at 13:15
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    @mplungjan No, as JBJ has already said "no dashes when used as a noun phrase". – TrevorD Aug 27 '13 at 14:25

Nouns are often used like adjectives. When used in this fashion, they are called noun adjuncts or attributive nouns.

For example

  • chicken soup
  • horse barn
  • baseball diamond

Proof of concept is either a noun (when written with dashes) or a noun phrase, either of which can be used adjectivally.

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    Are these correct? My proof-of-concept. (noun), My proof-of-concept implementation. (noun as adjective: noun adjunct), and My blue proof of concept. (noun phrase with proof of concept as head noun). – Daniel Aug 27 '13 at 13:37
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    The first two are fine. The last is grammatical, but makes no sense. But my first proof of concept would be fine. – bib Aug 27 '13 at 13:50
  • I was trying to use blue as means of identification (=noun?) and not as an adjective. My reasoning is that it would result in noun + head noun. The prototypes are color coded instead of using numerals: blue, yellow, green and so on. I don't know if that would make more sense though. – Daniel Aug 27 '13 at 14:00
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    Perhaps if fully laid out in context: I have run three proof of concept experiments, code-named Red, Blue and Yellow. The Blue proof of concept yielded the best results. The grammar holds. But blue in this context is a straight-up adjective. – bib Aug 27 '13 at 14:03
  • If we modify the sentence to My Blue proof of concept., is it a valid assumption the writer means to identify a specific proof of concept? Notice the capital B. – Daniel Aug 27 '13 at 14:16

Generally, It is correct to say

My proof-of-concept implementation

since you can have a "proof-of-concept implementation" and a "final implementation"

it is wrong to say

My proof-of-concept prototype

since you don't have "proof-of-concept prototype" and a "final prototype"

Unless your prototypes cost millions of dollars for each one. e.g. aerospace. Then you can have var. stages of the prototype itself. Otherwise, the prototype is a stage of a bigger process


I would suggest you modify your sentence as follows:

Successfully evaluated by proof of principle (/studies).

As used here, I don't think you should include 'a' in the sentence because proof of concept/principle studies are not specific examples - they are generalizable demonstrations. In the same way that it is wrong to use the word prototype.

Otherwise I don't think there is a problem with it being used as a noun or as an adjective. And I think the hyphens are optional as the three words always go together.

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