In the Roman Republic, the dictator (“one who dictates”), was an extraordinary magistrate  (magistratus extraordinarius) with the absolute authority to perform tasks beyond the authority of the ordinary magistrate (magistratus ordinarius). The office of dictator was a legal innovation originally named Magister Populi (Master of the People), i.e. Master of the Citizen Army.

The Roman Senate

Roman Senate

The Senate of the Roman Republic was a political institution in the ancient Roman Republic, however, it was not an elected body, but one whose members were appointed by the consuls, and later by the censors. After a magistrate served his term in office, it usually was followed with automatic...

 passed a senatus consultum authorizing the consul

Consul

Consul was the highest elected office of the Roman Republic and an appointive office under the Empire. The title was also used in other city states and also revived in modern states, notably in the First French Republic...

s to nominate a dictator — the sole exception to the Roman legal principles of collegiality

Collegiality

Collegiality is the relationship between colleagues.Colleagues are those explicitly united in a common purpose and respecting each other's abilities to work toward that purpose...

(multiple tenants in the same office) and responsibility (legal liability for official actions) — only one man was appointed, and, as the highest magistrate, he was not legally liable for official actions; 24 lictor

Lictor

The lictor was a member of a special class of Roman civil servant, with special tasks of attending and guarding magistrates of the Roman Republic and Empire who held imperium, the right and power to command; essentially, a bodyguard...

s attended him.

Only a single dictator was allowed, because of the imperium magnum, the great, extraordinary power with which he could over-rule, or depose

Deposition (politics)

Deposition by political means concerns the removal of a politician or monarch. It may be done by coup, impeachment, invasion or forced abdication...

 from office, or put to death

Capital punishment

Capital punishment, the death penalty, or execution is the sentence of death upon a person by the state as a punishment for an offence. Crimes that can result in a death penalty are known as capital crimes or capital offences. The term capital originates from the Latin capitalis, literally...

  other curule magistrates

Curule chair

In the Roman Republic, and later the Empire, the curule seat was the chair upon which senior magistrates or promagistrates owning imperium were entitled to sit, including dictators, masters of the horse, consuls, praetors, censors, and the curule aediles...

, also possessed of imperium

Imperium

Imperium is a Latin word which, in a broad sense, translates roughly as 'power to command'. In ancient Rome, different kinds of power or authority were distinguished by different terms. Imperium, referred to the sovereignty of the state over the individual...

.