To ostracise (or ostracize) a person is to exclude or banish (them) from a particular social group or the like. Sometimes ostracism serves as an emphatic expression of dislike or hostility towards the ostracised person, sometimes it is intended as an informal punishment – the ostracised person is considered to have done wrong or behaved badly. Both the verb and the noun are pronounced with the stress on the first syllable, (IPA: /'ɒs trə ,saɪz and 'ɒs trə ,sɪzm/).
The words ostracise and ostracism come from the Greek ὄστρακον (ostrakon), ‘an earthen vessel, a fragment of such a vessel, a potsherd’. In ancient Athens, in the absence of paper, ὄστρακα (ostraka), i.e., broken fragments of pottery, sometimes had the same function as the modern ballot paper: in particular, they were used as a means of voting in the procedure known as ὀστρακισμός (ostrakismos), ostracism.
Ostracism in ancient Athens
The institution of ostracism was a significant feature of Athenian democracy. Every year the citizen body had the opportunity to ostracise, or send into exile, a prominent public figure or politician. The name of the person one wished to ostracise was written on a shard of pottery, and the citizen most often named, above a certain minimum (probably 6000), was ostracised, i.e., banished from the territory of the state of Athens for a period of ten years. No social stigma attached to ostracism, the ostracised citizen was allowed to retain his property in Athens, and sometimes, if circumstances or sentiments changed, there would be an amnesty for those who had been ostracised and they would be permitted to return before ten years had elapsed.
Ostracism was introduced into the Athenian constitution in 507 BCE by the great lawgiver Cleisthenes (6th century BCE) after the period of rule by the ‘tyrants’ (or sole rulers) Pisistratus (ruled, though not continuously, 561-527 BCE) and his son Hipparchus (ruled 527-514 BCE): it was intended as a protection against ‘tyranny’, to be used pre-emptively against a citizen who had become too powerful and might be suspected of aiming to make himself a ‘tyrant’. Ostracism was initially used in the way Cleisthenes intended – the first person to be ostracised was a relative of Pisistratus in 487 BCE – but later it was sometimes misused to exile politicians who for whatever reason had made themselves unpopular. (See, e.g., Aristotle, Constitution of Athens, ch. 22.)