A noun can describe a noun after it just as adjectives can; it will not normally have an ending or an article of its own
HOW TO RECOGNIZE NOUNS USED AS ADJECTIVES
Just as adjectives can be used like nouns (see 6. Adjectives with no Noun 1: People-Naming), so nouns can be used like adjectives, especially in academic and professional writing. For a noun to be used like an adjective, it must be placed just before another noun, with no comma in between, and not mean the same as the other noun (see 77. Apposition). With this situation, it is sometimes hard to tell whether we have a noun or an adjective. Here are some examples of each to compare:
Adjectives Describing Nouns
HIGH PRICES, DIRTY OIL, AN OPEN DOOR, THE DAILY STRUGGLE, NUMEROUS DIFFICULT PROBLEMS
Nouns Describing Nouns
FUEL PRICES, ENGINE OIL, A CAR DOOR, THE FREEDOM STRUGGLE, WORD DEFINITION PROBLEMS
As the last example here shows, there can be more than one adjectival noun before another noun. A useful way to discover whether a word before a noun is an adjective or an adjectival noun is to reverse the two words and see if a preposition can be placed between them to obtain the same meaning, This is possible with adjectival nouns (prices of fuel, oil for engines, the door of a car, a struggle for freedom, and problems with the definition of words), but not adjectives (we cannot say *prices of high). For a discussion of the most typical prepositions, see 136. Types of Description by Nouns.
This test can even help if a particular word describing a noun is shown in the dictionary to be sometimes a noun and sometimes an adjective, like English, male or walking. We just have to rely on context or common sense to decide whether we have a noun or an adjective.
Consider the phrase English teacher. If English is a noun, the phrase means “a teacher of English”, telling us what the teacher teaches and not his/her nationality. However, if English is an adjective, the phrase means “a teacher who is English”, telling us nothing about the subject that the teacher teaches. Only the context of this phrase can tell us which meaning is intended (see 124. Structures with a Double Meaning).
There is a similar situation with the phrase male washroom, though logic as much as context indicates it must mean “washroom for males”, and not “washroom that is male”. Also similar is walking, which commonly occurs in walking wounded, walking stick and walking tours. It is an adjective in the first, a noun in the second (sticks do not walk!) and probably an adjective in the third (see 71. Gerund and Participle Uses of “-ing”).
PROBLEMS IN THE USE OF ADJECTIVAL NOUNS
1. Misreading Adjectival Nouns
2. Using the Wrong Article with Adjectival Nouns
When two nouns are paired together, which one determines whether the article before is the or a or nothing? What should the article be in this sentence?
(a) … world wealth has greatly increased.
The rule is that the article is determined by the last noun in a group, in this case wealth. Since wealth is uncountable, the article cannot be a. Since wealth has general meaning, the is also ruled out: a “zero” article must be used (see 110. Nouns without “the” or “a”).
The problem that many learners of English have is being influenced by the first noun, here world. Since this is a countable noun that nearly always has the (see 89. Using “the” with General Meaning), there is a temptation to write the even when the noun is adjectival. Article usage before adjectival nouns is a topic in my book Grammar Practice for Professional Writing, and is further illustrated in the posts 47. Article Errors with Proper Nouns and 138. Test Your Command of Grammar.
3. Confusing Adjectival Nouns and Nouns with an Apostrophe Ending
Nouns used like adjectives do not have an apostrophe ending, but sometimes they are very similar to nouns that do. This is the case, for example, with customer accounts, which could also be written with -s’ (customers’ accounts). The problem is that the choice is not always so free: sometimes it involves a significant meaning difference, sometimes an apostrophe ending is not possible at all, and sometimes it is the only possibility. An example of where a difference exists is with weekend work and a weekend’s work, the first meaning “work for weekends”, the second “work lasting a weekend”.
For errors to be avoided in this area, there is a need for a good knowledge of how apostrophe endings work. This is, unfortunately, a complex area, but within this blog some advice is available in the post 58. Optional Apostrophe Endings.
4. Using an Adjective Instead of an Adjectival Noun
Some past students of mine described their place of study as a “Philosophical Centre” when its correct name was “Philosophy Centre”. The difference is that the former, with an adjective, means that the centre itself is “philosophical” (just as the adjective English before teacher tells us what the teacher is), while the latter, with an adjectival noun, means that the centre is for Philosophy (in the same way as the noun English suggests a teacher of English).
Other examples of wrongly-used adjectives are healthy advice, industrial spokesperson and photographic workshop. Sometimes, however, there is a practically free choice between an adjective and an adjectival noun, e.g. autumn/autumnal colours, grammar/grammatical rules and manager/managerial vacancy.
5. Placing an Adjective before an Adjectival Noun
It is not an error to place an adjective before an adjectival noun, but there is a need to appreciate that such adjectives are capable of being linked with either of the two nouns after them, and might thus be understood as going with the wrong one (see 124. Structures with a Double Meaning). In many cases, the right interpretation is clear (e.g. in undesirable police accidents the adjective surely goes with the second noun), but in some it is less so (e.g. important customer accounts).
6. Making Adjectival Nouns Plural
Most adjectival nouns are singular in form even when their meaning is plural. This was clear among the earlier examples, where engine in engine oil became plural engines in the non-adjectival oil for engines, and word in word definition problems became plural words in problems with the definition of words. This trend holds even when an adjectival noun has a number before it, as in a two-hour meeting or a six-page essay.
However, not all adjectival nouns are singular. Examples where plurals occur are a Beatles record, the Roads Minister, materials design, a mathematics department, a solutions group, sales performance, a careers adviser, the arms race and a Masters degree. The rest of this discussion focuses on this problem.
WHEN SHOULD ADJECTIVAL NOUNS BE PLURAL?
There seems to be no single rule in answer to this question, but rather a list of rules. An easy one to remember involves nouns that have no singular form, such as those in mathematics department (and other phrases with –ics subject names like economics), customs officer, sports day and Masters degree. If these have no singular, their adjectival forms have to be plural.
The other main reason for making an adjectival noun plural rather than singular seems to be a need to avoid ambiguity. One type is simple singular/plural ambiguity. Consider the phrase Beatles records. If we said Beatle records instead, we might be misunderstood as referring to records by individual Beatles, such as John Lennon or Paul McCartney, who made many records by themselves as well as with the other three Beatles. Thus there is the option of using the plural adjectival form in order to make it clear that all of the Beatles are meant. In the same way, we might prefer to say a solutions group instead of a solution group in order to make it clear that the group was concerned with solutions to many problems and not just one.
A slightly different type of ambiguity that using a plural adjectival noun can overcome involves nouns with variable countable and uncountable meanings, such as material. Uncountably this word means something that can be used to create something else, such as wood used for making doors or photographs used to tell a story. Used countably as a plural, however, it often means “written explanations and exercises for learning”. If this word was always used in the singular form when adjectival, we would not always be able to tell whether the countable or uncountable usage was intended, since the main indicators of countability (article a, plural –s ending) are both normally disallowed with adjectival nouns. If it was important to clarify that a countable meaning was intended, the use of the plural form would be one way to do it, as in materials design.
Numerous other nouns can vary like material (see 23. Noun Countability Clues 3). Adjectival uses that similarly include -s include languages department (signalling many languages are studied, rather than language in general) and metals extraction (emphasising that more than a single type of metal is extracted).
The phrase a careers adviser is perhaps associated with yet another type of ambiguity. It would appear that using a singular adjectival noun (a career adviser) changes the preposition link between the two nouns. Instead of meaning “a person who gives advice about careers”, it seems to mean “a person who gives advice by career”. The reason why this interpretation is more natural could be because the noun career is actually quite often used in this singular adjectival sense to mean “by career”. Examples are career writer, career footballer and career lawyer. Alternative implied prepositions are quite common (see 136. Types of Description by Nouns). They will not always match the choice between a singular and a plural adjectival noun, but they will sometimes.
Thus, adjectival nouns are fraught with pitfalls, and do not fail to produce errors in the writing of advanced learners of English. Studying their various properties is hence likely to be well worth the effort.