The chreia was, in antiquity

Classical antiquity

Classical antiquity is a broad term for a long period of cultural history centered on the Mediterranean Sea, comprising the interlocking civilizations of ancient Greece and ancient Rome, collectively known as the Greco-Roman world...

 and the Byzantine Empire

Byzantine Empire

The Byzantine Empire was the Eastern Roman Empire during the periods of Late Antiquity and the Middle Ages, centred on the capital of Constantinople. Known simply as the Roman Empire or Romania to its inhabitants and neighbours, the Empire was the direct continuation of the Ancient Roman State...

, both a genre of literature and one of the progymnasmata

Progymnasmata

Progymnasmata are rhetorical exercises gradually leading the student to familiarity with the elements of rhetoric, in preparation for their own practice speeches and ultimately their own orations.Both Hermogenes of Tarsus and Aelius Festus Aphthonius wrote treatises containing progymnasmata...

.

Definition

A chreia was a brief, useful ("χρεία" means useful) anecdote about a particular character. That is, a chreia was shorter than a narration—often as short as a single sentence—but unlike a maxim, it was attributed to a character. Usually it conformed to one of a few patterns, the most common being "On seeing..." (ιδών or cum vidisset), "On being asked..." (ἐρωτηθείσ or interrogatus), and "He said..." (ἔθη or dixit).

Examples

The following chreia, the most common in ancient sources, is illustrative:
Chreiai could be silly:
Or solemn:
Wise:
Or witty:
Or all of these:
As a literary genre the chreia was a subject of collection. Scholars such as Plutarch

Plutarch

Plutarch then named, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. 46 – 120 AD, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...

 or Seneca

Seneca the Younger

Lucius Annaeus Seneca was a Roman Stoic philosopher, statesman, dramatist, and in one work humorist, of the Silver Age of Latin literature. He was tutor and later advisor to emperor Nero...

 kept their own private collections of chreiai. Published collections were also available. The chreia is primarily known, however, for its role in education. Students were introduced to simple chreiai almost as soon as they could read. Later they practiced the complex grammar of Greek by putting these chreiai through changes of voice

Voice (grammar)

In grammar, the voice of a verb describes the relationship between the action that the verb expresses and the participants identified by its arguments . When the subject is the agent or doer of the action, the verb is in the active voice...

 and tense

Grammatical tense

A tense is a grammatical category that locates a situation in time, to indicate when the situation takes place.Bernard Comrie, Aspect, 1976:6:...

. As one of the last stages in their preparation for rhetoric—this is where chreiai serve as one of the progymnasmata—they would elaborate the theme of a chreiai into a formal eight-paragraph essay. The student would praise, paraphrase, explain, contrast, compare, provide an example, make a judgment, and, in conclusion, exhort the reader.