Consul - highest elected office of the Roman Republic, which became an appointive office under the Empire. Under the Republic the minimum age of election to consul for patricians was 40 years of age, for plebeians 42. Two consuls were elected each year, they served together with veto power over each other's actions, and the year of their service was known by their names. For instance, the year we commonly call 59 B.C.E. was called by the Romans "the year of Caesar and Bibulus," since the two colleagues in the consulship were Julius Caesar and Marcus Calpurnius Bibulus. "Consules" in Latin means "those who walk together".
see Cursus honorum - sequence of offices