【正确答案】：
     IT IS NOT UNUSUAL TO HAVE NOUNS CONVERTED FROM ADJECTIVES. UNLIKE VERBS, NOT ALL ADJECTIVES WHICH ARE CONVERTED CAN ACHIEVE A FULL NOUN STATUS. SOME ARE COMPLETELY CONVERTED, THUS KNOWN AS FULL CONVERSION, OTHERS ARE ONLY PARTIALLY CONVERTED, HENCE PARTIAL CONVERSION. 
     A NOUN FULLY CONVERTED FROM AN ADJECTIVE HAS ALL THE CHARACTERISTICS OF NOUNS AND CAN TAKE AN INDEFINITE ARTICLE OR –(E)S TO INDICATE SINGULAR OR PLURAL NUMBERS, SUCH AS A WHITE, VALUABLES. 
     BUT NOUNS PARTIALLY CONVERTED FROM ADJECTIVES DO NOT POSSESS ALL THE QUALITIES A NOUN DOES. THEY MUST BE USED TOGETHER WITH DEFINITE ARTICLES. THEY RETAIN SOME OF THE ADJECTIVE FEATURES, FOR EXAMPLE, THE POOR, THE RICH.
【题目解析】：名词从形容词转换而来并不罕见。不同于动词，不是所有被转换的形容词都能达到完全的名词状态。有些是完全转换的，因此称为完全转换，而另一些只是部分转换，因此是部分转换。完全从形容词转换而来的名词具有名词的所有特征，可以采用不定冠词或–s来表示单数或复数，如drinkables（饮料）。但是名词部分地从形容词转换而得不到名词的所有性质。它们必须与定冠词一起使用。它们保留了一些形容词的特征，例如，the poor（穷人）和the rich（富人）。