23. Noun Countability Clues 3: Subtypes


Countable Subtypes of "Fuel"

Countable Subtypes of “Fuel”


Some substance nouns are used countably to suggest subdivisions of the substance, and uncountably otherwise


Being able to recognise whether nouns are “countable” or “uncountable” is an important requirement for using them in a grammatically correct way. Indeed, it is so important that noun countability is an aspect of English that even learners at the most elementary level are likely to have encountered. However, it also an aspect of English that continues to give trouble right up to the most advanced levels. It is this fact that is behind the present post. This is the third of four within these pages that aim to help out with some of the problems. The three others are 14. Noun Countability Clues 1: Action Outcomes,  19. Noun Countability Clues 2: Activity Locations and 43. Noun Countability Clues 4: Substance Locations.

Most readers will know that the terms “countable” and “uncountable” refer not to what nouns mean but to what they do. They tell us not about the ability or otherwise of the thing expressed by the noun to “be counted”, but rather about the grammar rules that the noun must follow. Only “countable” nouns, for example, can be made plural. Only “uncountable” nouns can be singular without an article. “Uncountable” nouns cannot go after each; singular countable ones cannot go after enough. For more, see 81. Tricky Word Contrasts 2, #9 and 110. Nouns without “the” or “a”).

The reason for calling these two types of noun “countable” and “uncountable” is that this was in the past believed to be a useful guide for recognising which nouns are which: it is nice and simple to suggest that if a noun represents something that can be counted, it is “countable”, otherwise not. The problem, however, is that much confusion results. Some nouns, like money, represent an obviously countable idea, but are not “countable”; while others, like accommodation, represent ideas whose ability to be counted seems different to different people.

Evidence of the subjectivity of “ability to be counted” is provided by the existence of some “uncountable” nouns in English that are “countable” in French, a language with a similar way of classifying nouns. Examples are access, advice, information and research. Moreover, there are some English nouns that speakers of languages with no countability distinction at all typically judge incorrectly (e.g. *luggages, *punctuations).

So what better way is there of determining countability in English? As with the transitivity of verbs (see 113. Verbs that cannot be Passive), the surest way is to find out from a dictionary. Failing that, however, the kind of meaning possessed by the noun still seems to be the best clue. Ability to be counted can on occasion be helpful, and there is also some value in the common assertion that many uncountable nouns like flour and water represent a “mass” of something, with no fixed shape, rather than something discrete.

However, there is another possibility too, which is not usually highlighted in grammar books. A very large number of nouns are sometimes countable and sometimes uncountable, depending on their meaning, and the difference between the two meanings rarely has anything to do with ability to be counted or with shape. It is not always the same kind of difference, but some kinds can occur across numerous nouns that have variable countability. There thus seems to be value in making these kinds of difference clear and indicating the nouns that possess them.

At least four major kinds of difference seem to be possible between the countable and uncountable meanings of individual nouns. This post is about one of these four: a “substance” meaning when the noun is uncountable versus a “subtype” meaning of the countable form. The other three meaning differences are the topics of the three similar posts to this that are indicated above.



A substance is a physical material – solid, liquid or gas – that has no particular or permanent shape. Substances are generally not objects. Most nouns representing substances have an uncountable use. Examples are acid, butter, charcoal, electricity, food, fuel, iron, paper, petrol, plastic, sugar, water and wheat.

Many substances can be divided into subtypes. Fuel, for example, includes charcoal, petrol, diesel and kerosene. The names of divisible substances like fuel tend to have a countable use as well as an uncountable one. We can collectively refer to all of the types of fuel just listed as fuels just as easily as fuel, and each of them can also be individually called a fuel. Other substance names like this include food, stone, sugar and wood.

If it is true that substance nouns can be used both countably and uncountably when they represent divisible substances, when is the countable use preferable? The answer, I think, is when the existence of different subtypes is important to what we are saying. Consider this:

(a) The price of fuel varies.

Suppose that the cause of price variation was the kind of fuel being used (e.g. petrol being more expensive than kerosene). Then the existence of subtypes would be important, and it would be better to say fuels than fuel. With uncountable fuel (singular without a or the), the reader is more likely to consider other causes of varying prices, such as the provider. This is because the existence of fuel subtypes would not be highlighted. To take another example:

(b) Fuel is necessary for machines to function.

We could again say fuels are instead of fuel is here, but that would be unusual because the existence of types of fuels is not obviously relevant to the point being made.

The suggestion and non-suggestion of subtypes by means of countable and uncountable usage is also found with many abstract nouns, such as doubt, fact, illness, opportunity, quality and strength. A problem with abstract nouns, however, is that those with the double usage are harder to identify because they seem to lack a recognisable feature that is comparable to the substance nature of concrete nouns. We need such a feature because there are certainly some abstract nouns that might be expected to have the double usage but do not. Consequence, for example, is nearly always countable and patience is typically uncountable.



Here are some more examples of nouns like the above. Try naming some of the subtypes implied in each case by the countable usage:

(a) colour, (a) difficulty, (a) food, (a) fruit, (an) industry, (a) language, (a) metal, (a) philosophy, (a) power, (a) science, (a) sky, (a) society, (a) stone, (an) understanding, (a) virtue, (a) wood.

A problem with some of these is that they can express even more meanings than the two being considered here. Stones are not always types of stone (exemplified by marble), but also small, roundish objects made out of that substance, whose type does not matter. In this sense, they are “substance locations” (see 43. Noun Countability Clues 4). In the same way, powers are not only types of power (e.g. the power to authorise a payment) but also powerful countries, places where power is located; and woods are either types of wood (e.g. mahogany) or places where it is located in the form of trees.

Slightly different is the uncountable industry, which can express not only the general meaning of “industrial companies” (as in Industry is unhappy), but also the activity meaning of “hard work” (as in Industry will be rewarded). This means that the countable form an industry is both a subtype and an activity location (see 19. Activity Locations).

Finally, it is worth noting the exceptional contrast between salt and a salt. We would expect salt to mean any substance with the properties of a saltthe same meaning as salts but not highlighting the existence of subtypes. Thus, sodium chloride and potassium chloride should both be describable as either “salt” or “salts” just as coal and oil can both be called either “fuel” or “fuels”. In fact, however, salt means only sodium chloride (the type you put on your food with pepper). If we want to generalise about all substances similar to it, we can only say salts.

Now here is an exercise offering further practice with nouns that can highlight subtypes by being used countably. Answers are given after it.



In the following sentences, which show countable and uncountable meanings of the same word, one space needs a(n) and one does not. Decide where a(n) should go each time (answers below).


1. Cars need ………. fuel, but petrol is ………. expensive fuel.

2. ………. metal that does not behave like ………. metal is mercury.

3. Most people have ………. personal philosophy not based on ………. philosophy.

4. ………. society can change if ………. society within it changes.

5. Care is needed when choosing ………. colour for internal decoration, in order to avoid a clash of ………. colour overall.

6. ………. wood is suitable for furniture-making, and oak is ………. particularly beautiful and durable wood.


ANSWERS:  A(n) should go in the first space in 2,3 and 5, and in the second in 1, 4, and 6.


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