When should I use the plural form 'fossil fuels' and when the singular form?

Isn't fuel uncountable? Why do we ever use its plural form?

  • 3
    You have given no examples, no context. The term “fossil fuels” relates to different types of fuel, all of which have have a prehistoric, biological origin: coal, oil, and natural gas. What is your source for the assertion that “fuel” in this sense is a mass noun? Sep 21, 2022 at 9:03
  • @JeffMorrow I have no clear idea about that, so I asked here.
    – Michael
    Sep 21, 2022 at 9:09
  • 2
    “Fuel” is one of those words such as “water” that is sometimes a mass noun and sometimes a countable noun. Sep 21, 2022 at 9:40

1 Answer 1


Fossil fuels is like fish. If there are different kinds, then use the plural form.

  • There are many fish in the trout hatchery.
  • He caught fishes of many types, bass and trout and perch.
  • The coal-fired generating plant used thousand of tonnes of fossil fuel.
  • The well provides both petroleum and natural gas, both fossil fuels.
  • I agree about fuels, but not about fishes. Fish can be a mass noun when it is a foodstuff (I had some fish) and in that use it can take a plural for kinds of fish (We have three fishes on the table, salmon, cod, and plaice). But outside of that, fish is not a mass noun, it is a count noun that happens to have a plural which is the same as its singular (as well as another plural which is different). Myself I rarely use fishes to refer to animals, I almost always say fish; but I doubt that anybody uses fishes distinctively when they happen to be of different kinds.
    – Colin Fine
    Sep 21, 2022 at 16:42

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