形容詞可以用作主語,往往成對使用,具有名詞化的特點。例如: Old and young joined in the discussion . Rich or poor meant the same to him . Care f ul and careless are as different as fire and water . Wet or dry will make little difference to them . Note:形容詞還可用作賓語。例如: They can't tell right from wrong . Children should be taught to know good from bad . ——《大學英語語法講座與測試》（第二版）

在英語中，形容詞主要作定語，表語和補足語。例如：We have a beautiful school. Our school is beautiful. We'll make our school more beautiful. 動態形容詞也可作伴隨或補充說明狀語。例如: The dog lay on the floor, dead. 形容詞一定要作主語的話，就在其前邊加上being或to be。Being happy is happiness. 處在幸福中就是幸福。

一般情況下，英語中形容詞在句子中不能用於作主語。形容詞在句子中的功能主要用於作定語和表語。但是有部分形容詞之前加上定冠詞the之後，表示某一類人，可以用於作主語，比如，the poor(窮人)，the rich(富人)，the young(年輕人)，the old(老人)等。