Unlike most adjectives, which modify nouns, a substantive adjective is used to replace a noun. Often seen in ancient Greek and Latin, these adjectives are used in many modern languages as well. They have limited uses, however, in languages such as English, which do not indicate gender, case, or number by changing the spelling of the adjective itself. The word "substantive" is of Latin origin and means "standing in place of."
Normally an adjective is a word that modifies a noun in order to provide increased description or detail to that noun. Depending on the language, adjectives usually immediately precede or follow the nouns they are modifying. For example, in the phrases "the yellow car" and "the quick fox," the words "yellow" and "quick" are the adjectives.
A substantive adjective, however, does not modify a noun in a sentence, it replaces the noun. Therefore, a substantive adjective can only be successfully used when the noun in question is understood without being explicitly stated. In Latin, Greek, and a number of modern languages, the adjective itself will offer information about the noun's gender and number by a change in spelling. The noun's case, or its function in the sentence, may also be indicated by the adjective's spelling. These spelling changes help give information about the noun in question even when it is not present in the sentence.
In English, however, adjectives do not change spelling based on whether the noun is singular or plural, nor do they show gender. Without having the number and gender explicitly stated, the use of the substantive adjective is limited. Despite this limitation, these adjectives are still frequently used. The noun being replaced is normally understood to be plural and to mean "people" or "things," depending on the overall context of the sentence.
For example, in the sentence "there is a gulf between the rich and the poor," both "rich" and "poor" are substantive adjectives. Here, they refer to people rather than things. The reader determines the correct nouns simply through context clues and a general understanding that people rather than objects are usually considered rich or poor. In the sentence, "we work to separate the good from the evil," the words "good" and "evil" are the substantive adjectives. Here, the words could mean either people or things, and if seen in a larger work, the reader may need to rely on context clues from the surrounding sentences to understand whether the author was referring to people or objects.