Answer : There are several terms in the English language that don’t change and can be used the same as nouns and adjectives.
Poor is one such word. The noun form for poor does not change, it is poor only.
For example- The poors of the the society do not enjoy the privileges of the rich in a society.
Poor has also the noun form, termed as ‘poverty’. For example: Poverty has become a huge problem in our society.