Roman inscription on Trajan's Column.

The native language of the Romans was Latin, an Italic language the grammar of which relies little on word order, conveying meaning through a system of affixes attached to word stems. Its alphabet was based on the Etruscan alphabet, which was in turn based on the Greek alphabet. Although surviving Latin literature consists almost entirely of Classical Latin, an artificial and highly stylized and polished literary language from the 1st century BC, the actual spoken language of the Roman Empire was Vulgar Latin, which significantly differed from Classical Latin in grammar and vocabulary, and eventually in pronunciation.

While Latin remained the main written language of the Roman Empire, Greek came to be the language spoken by the well-educated elite, as most of the literature studied by Romans was written in Greek. In the eastern half of the Roman Empire, which later became the Byzantine Empire, Latin was never able to replace Greek, and after the death of Justinian Greek became the official language of the Byzantine government. The expansion of the Roman Empire spread Latin throughout Europe, and over time Vulgar Latin evolved and dialectized in different locations, gradually shifting into a number of distinct Romance languages.

Although Latin is an extinct language with very few remaining fluent speakers, it remains in use in many ways, such as through Ecclesiastical Latin, the traditional language of the Roman Catholic Church and the official language of the Vatican City. Additionally, even after fading from common usage Latin maintained a role as western Europe's lingua franca, an international language of academia and diplomacy. Although eventually supplanted in this respect by French in the 19th century and English in the 20th, Latin continues to see heavy use in religious, legal, and scientific terminology—it has been estimated that 80% of all scholarly English words derive directly or indirectly from Latin.