An uncountable noun cannot be made plural. See also Singular/ Plural Noun.

In example 1, “media” is already a plural noun, representing the plural form of medium.  In example 2, the uncountable noun “research” appears in the plural form.

 

WRONG
RIGHT

Today’s teenagers have grown up with medias and the internet.

Today’s teenagers have grown up with media and the internet.

With the reference from the above researches, people believe that healthy living in Hong Kong has been declining.

With the reference from the above research, people believe that healthy living in Hong Kong has been declining.

See more.

Click here for an exercise on countable/ uncountable nouns.

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