Using a word which is not a noun as a noun is called nominalization. In Persian, adjectives can be nominalized and function exactly like nouns. They are called nominalized adjectives or adjectival nouns. Nominalized adjectives can take plural suffix like a noun and have plural form. In English, adjectives are nominalized with the definite article. However, they are not exactly treated like a noun and do not take plural suffix.

Adjective Adjectival Noun
زخمی
zakhmi
wounded
زخمیها
zakhmihâ
the wounded
بیکار
bikâr
unemployed
بیکاران
bikârân
the unemployed
سوئدی
Suedi
Swedish
سوئدیها
Suedihâ
the Swedish

In the following examples, nominalized adjectives are in singular form:

خوب، بد، زشت
khub, bad, zesht
the good, the bad, and the ugly
دارا و ندار
dârâ vo nadâr (dârâ o nadâr)
the rich and the poor