The colloquial speech of cultured Romans appears in the works of various writers, notably in the comedies of Plautus and Terence, the letters of Cicero, the Satires and Epistles of Horace, and the Satyricon of Petronius Arbiter. It is characterized by freedom of syntax, by the presence of numerous interjections, and by the frequent use of Greek words. This colloquial speech of polite society (sermo cotidianus) is not to be confused with the sermo plebeius, the language of the uneducated classes, which shows a greater disregard for syntax, a love of new words, and a striving for simplicity, especially in word order. The sermo plebeius is known as Vulgar Latin, a term that sometimes includes the sermo cotidianus of the more educated Romans. The Romance languages developed not from the literary Latin language but from the sermo plebeius of the Late Latin period, when it was also known as lingua Romana. For instance, equus (“horse”) fell out of use, and caballus (“nag,””packhorse”) provided the Romance words for horse (cheval, caballo); similarly, the Romance word for head (tête, testa) comes not from Latin caput, but from a Latin slang word for head (testa), literally “pot.”