The use of adjectives as nouns is common in Latin, from which some of our vocabulary and forms derive.

Ave Imperator, morituri te salutant (Hail Emperor, those who are about to die salute you)

Morituri is actually a participle form, used as an adjective, and could be translated literally the about to be dying.

Using adjectives as nouns in English has been common for some time.

Only the good die young

(No, Billy Joel did not coin the phrase.)

This is more often found with either a definite or indefinite article.

The evil that men do lives after them; The good is oft interred with their bones.

Marc Antony in Shakespeare's Julius Caesar

The use of adjectives as nouns is common in Latin, from which some of our vocabulary and forms derive.

Ave Imperator, morituri te salutant (Hail Emperor, those who are about to die salute you)

Morituri is actually a participle form, used as an adjective, and could be translated literally the about to be dying.

Using adjectives as nouns in English has been common for some time.

Only the good die young

(No, Billy Joel did not coin the phrase. Wordsworth said O Sir! the good die first, And they whose hearts are dry as summer dust Burn to the socket. This has morphed over time to the simpler phrase.)

This is more often found with either a definite or indefinite article.

The evil that men do lives after them; The good is oft interred with their bones.

Marc Antony in Shakespeare's Julius Caesar