I'm reading The Wind in the Willows by Kenneth Grahame and there's the following phrase: "They were a powerful people, and rich, and great builders."
However, I've googled a rule: Plural nouns can be used with the definite article or no article at all; to use an indefinite article would be incorrect.
Does it mean that "people" here is a singular noun? Is this because the phrase refers to people as a tribe/community?