When the words "Canadian, American, Australian and Brazilian" refer to people,

When the words "Canadian, American, Australian and Brazilian" refer to people,

There are two cases
These words can be used as both adjectives and nouns. When they are nouns, they all have plural forms, such as two Canadians. When they are adjectives, they mean "of". When they are expressions in sentences, they often translate into ". People", such as they are Canadians, They are Canadians