In
grammar, a
noun adjunct or
attributive noun or
noun (
pre)
modifier is an optional
noun that
modifies another noun; it is a noun functioning as an
adjective. For example, in the phrase "chicken soup" the
noun adjunct "chicken" modifies the noun "soup". It is irrelevant whether the resulting
compound noun is spelled in one or two parts. "Field" is a noun adjunct in both "field player" and "fieldhouse".
[1]Swan* describes typical uses of noun + noun structures. In part, he states:"The noun + noun structure is mostly used to make 'classifying' expressions which name a particular type of thing.mountain plants (a special group of plants) [Rachel notes NOT 'mountainous plants.'....]We use noun + noun especially to talk about things that belong to common well-known classes (so that the two nouns really describe a single idea)...history book (a common class of book) [Rachel notes NOT '[atrike]historical book[/strike]']He was reading a book about the moon. (NOT a moon book ...."At the end of his relatively long description of advanced points of noun + noun, Swan says:"This is a very complicated area of English grammar. The 'rules' given above show the general patterns, but unfortunate there is no easy way to be quite sure which structure is used to express a particular compound idea. The most common expressions will be learnt by experience; in cases of doubt, a good dictionary will often show shich form is correct."Swan's comments are, perhaps, directed at learners way below those of us discussing this topic. However, they serve to remind us that the 'rules' are guidelines.I personally think that Fowler's directive to prefer an adjective, if one exists, instead of a noun, strikes me as being unnecessarily prescriptive._______*Practical English Usage, Third Edition, by Michael Swan. Oxford 2005.(noun + noun), sections 385-386