Yes, they are both nouns, and yes "the British" is common.
Student or Learner
He brightened the lives of Americans and British through the hard years.
My question is "Are both 'Americans' and 'British' nouns?" in this sentence.
As far as I know, when used as a noun, "British" should be "the British" to mean the whole group.
Thanks for help!
I don't know who he is, but maybe he didn't brighten the lives of the whole group, just some people of those nationalities.
Seem to me to be the place to use the word "Britons." Maybe that's considered old fashioned?
"British" is an adjective. "The British" is the people.