Latin.
In the history of languages, Latin originated in the Latium region of the Italian Peninsula around the 8th century BC, initially spoken by local peoples. Simultaneously, in the region of Ancient Greece, Greek was developing, a language of great importance to philosophy, science, and the arts.
With the expansion of the Roman Empire, Latin spread to various regions, becoming the main administrative and cultural language. However, Greek was already widely used in the east of the empire, especially in areas previously conquered by Alexander the Great. Thus, for a long time, Latin and Greek coexisted: Latin predominated in the West, while Greek was more common in the East.
Latin had different forms, such as Classical Latin, used by authors like Cicero and Virgil, and Vulgar Latin, spoken in everyday life. Greek also had variations, such as Classical Greek and Koine Greek, which became a more common and widespread form, even being used in important texts of the time.
Regarding their function, both Latin and Greek are inflected languages, meaning that words change form according to their function in the sentence. Both use grammatical cases, which allows for greater freedom in word order. Verbs also exhibit many variations, indicating tense, mood, person, and number.
Even after the fall of the Roman Empire, Latin continued to be used in the West, mainly by the Church and scholars, while Greek remained strong in the East, especially in the Byzantine Empire.
Thus, Latin and Greek were fundamental to the cultural, scientific, and philosophical formation of the Western world, profoundly influencing the knowledge we have to this day.