The noun "gas" can be both countable and uncountable.
Meaning: any substance like air that's neither solid nor liquid
Example sentence: Did you know that a cow emits around 200 litres of gas a day by burping?
Meaning: a particular type of gas
Example sentence: Cows emit methane, one of the many gases that cause global warming.
Note: In American English, another uncountable meaning of "gas" is petrol, a liquid fuel for cars (derived from "gasoline").
Test your understanding:
- How many different gases are in the atmosphere?
- How much gas does a sheep emit when it burps?