The legacy of the Roman Empire has been varied and significant. The Roman Empire, built upon the legacy of other cultures, has had long-lasting influence with broad geographical reach on a great range of cultural aspects, including state institutions, law, values, religious beliefs, technological advances, engineering and language.
This legacy survived the demise of the empire (5th century AD in the West, and 15th century AD in the East) and went on to shape other civilisations, a process which continues. Rome was the "civitas" (reflected in the etymology of the word "civilisation") and connected with the actual western civilisation on which subsequent cultures built is the Latin language of ancient Rome, epitomized by the Classical Latin used in Latin literature, which evolved during the Middle Ages and remains in use in the Roman Catholic Church as Ecclesiastical Latin. Vulgar Latin, the common tongue used for regular social interactions, evolved simultaneously into Romance languages that still exist, notably Italian, French, Spanish, Portuguese, Romanian. Although the Western Roman Empire fell in the 5th century AD, the Eastern Roman Empire continued until its conquest by the Ottoman Empire in the 15th century AD and cemented the Greek language in many parts of the Eastern Mediterranean even after the Early Muslim conquests of the 7th century AD. Roman paganism was largely displaced by Roman Catholic Christianity after the 4th century AD and the Christian conversion of Roman emperor Constantine I (r. 306–337 AD). The Christian faith of the late Roman Empire continued to evolve during the Middle Ages and remains a major facet of the religion and the psyche of the modern Western world.
Ancient Roman architecture, largely indebted to ancient Greek architecture of the Hellenistic period, has influenced the architecture of the Western world, particularly during the Italian Renaissance of the 15th century. Roman law and republican politics (from the age of the Roman Republic) have left an enduring legacy, influencing the Italian city-state republics of the Medieval period, as well as the United States and other modern democratic republics. The Julian calendar of ancient Rome formed the basis of the standard modern Gregorian calendar, while Roman inventions and engineering, such as the construction of concrete domes, continued to influence various peoples after the fall of Rome. Roman models of colonialism and warfare became influential.
Language.
Latin became the lingua franca of the early Roman Empire and later of the Western Roman Empire, while – particularly in the Eastern Roman Empire – indigenous languages such as Greek and to a lesser degree Egyptian and Aramaic language continued in use. Despite the decline of the Western Roman Empire, the Latin language continued to flourish in the very different social and economic environment of the Middle Ages, not least because it became the official language of the Roman Catholic Church. Koine Greek, which served as a lingua franca in the Eastern Empire, remains in use today as a sacred language in some Eastern Orthodox churches.
In Western and Central Europe and in parts of northern Africa, Latin retained its elevated status as the main vehicle of communication for the learned classes throughout the Middle Ages and subsequently; witness especially the Renaissance and Baroque periods. Books which had a revolutionary impact on science, such as Nicolaus Copernicus' "De revolutionibus orbium coelestium" (1543), were composed in Latin. This language was not supplanted for scientific purposes until the 18th century, and for formal descriptions in zoology as well as botany it survived to the later 20th century. The modern international binomial nomenclature holds to this day: taxonomists assign a Latin or Latinized name as the scientific name of each species.
In the 21st century the Romance languages, which comprise all languages that descended from Latin, are spoken by more than 920 million people as their mother tongue, and by 300 million people as a second language, mainly in the Americas, Europe, and Africa. Romance languages are either official, co-official, or significantly used in 72 countries around the world. Of the United Nations' six official languages, two (French and Spanish) descend from Latin.
Additionally, Latin has had a great influence on the lexicon of West Germanic languages. Romance words make respectively 59%, 20% and 14% of English, German and Dutch vocabularies. Those figures can rise dramatically when only non-compound and non-derived words are included. Accordingly, Romance words make roughly 35% of the vocabulary of Dutch. Of all the loanwords in Dutch, 32.2% come directly from some form of Latin (excluding loans from Romance languages). Over 60% of Albanian vocabulary consist of Latin roots, causing Albanian to once have been mistakenly identified as a Romance language.
Script.
All three official scripts of the modern European Union—Latin, Greek and Cyrillic—descend from writing systems used in the Roman Empire. Today, the Latin script, the Latin alphabet spread by the Roman Empire to most of Europe, and derived from the Phoenician alphabet through an ancient form of the Greek alphabet adopted and modified by Etruscan, is the most widespread and commonly used script in the world. Spread by various colonies, trade routes, and political powers, the script has continued to grow in influence. The Greek alphabet, which had spread throughout the eastern Mediterranean region during the Hellenistic period, remained the primary script of the Eastern Roman Empire through the Byzantine Empire until its demise in the 15th century. Cyrillic scripts largely derive from the Greek.
Latin literature.
The Carolingian Renaissance of the 8th century rescued many works in Latin from oblivion: manuscripts transcribed at that time are our only sources for some works that later fell into obscurity once more, only to be recovered during the Renaissance: Tacitus, Lucretius, Propertius and Catullus furnish examples.
Other Latin writers never went out of circulation: Virgil, reinterpreted as a prophet of Christianity by the 4th century, gained the reputation of a sorcerer in the 12th century.
Cicero, in a limited number of his works, remained a model of good style, mined for quotations. Medieval Christians read Ovid allegorically, or re-imagined Seneca as the correspondent of Saint Paul. Lucan, Persius, Juvenal, Horace, Terence, and Statius survived in the continuing canon and the historians Valerius Maximus and Livy continued to be read for the moral lessons history was expected to impart.
Through the Roman Empire, Greek literature also continued to make an impact in Europe long after the Empire's fall, especially after the recovery of Greek texts from the East during the high Middle Ages and the resurgence of Greek literacy during the Renaissance. Many educated Westerners from the Renaissance up to the 20th century, for instance, read Plutarch's "Lives of the Noble Greeks and Romans", originally written in Greek. Shakespeare's play "Julius Caesar" takes most of its material from Plutarch's biographies of Caesar, Cato, and Brutus, whose exploits were frequently discussed and debated by the literati of Shakespeare's time.
Education.
Martianus Capella developed the system of the seven liberal arts that structured medieval education. Although the liberal arts were already known in Ancient Greece, it was only after Martianus that the seven liberal arts took on canonical form.
His single encyclopedic work, "De nuptiis Philologiae et Mercurii" "On the Marriage of Philology and Mercury", laid the standard formula of academic learning from the Christianized Roman Empire of the 5th century until the Renaissance of the 12th century.
The seven liberal arts were formed by the trivium, which included the skills of grammar, logic, and rhetoric, while arithmetic, geometry, music, and astronomy played part as the quadrivium.
Calendar and measurement.
The modern Western calendar is a refinement of the Julian calendar, which was introduced by Julius Caesar. The calendar of the Roman Empire began with the months Ianuarius (January), Februarius (February), and Martius (March). The common tradition to begin the year on 1 January was a convention established in ancient Rome. Throughout the medieval period, the year began on 25 March, the Catholic Solemnity of the Annunciation.
The 5th-century Roman monk Dionysius Exiguus devised the modern dating system of the Anno Domini (AD) era, which is based on the reckoned year of the birth of Jesus, with AD counting years from the start of this epoch, and BC denoting years before the start of the era.
The modern seven-day week follows the Greco-Roman system of planetary hours, in which one of the seven heavenly bodies of the Solar System that were known in ancient times—Saturn, Jupiter, Mars, the Sun, Venus, Mercury and the Moon—is given "rulership" over each day. The Romance languages (with the exception of Portuguese, that assigns an ordinal number to five days of the week, from Monday to Friday, beginning with ', and ending with ') preserve the original Latin names of each day of the week, except for Sunday, which came to be called "" (Lord's Day) under Christianity.
Hours of the day.
The 12-hour clock is a time convention popularized by the Romans in which the 24 hours of the day are divided into two periods. The Romans divided the day into 12 equal hours, A.M. ("ante-meridiem", meaning before midday) and P.M. ("post-meridiem", meaning past midday). The Romans also started the practice used worldwide today of a new day beginning at midnight.
Numerals and units.
Roman numerals continued as the primary way of writing numbers in Europe until the 14th century, when they were largely replaced in common usage by Hindu–Arabic numerals. The Roman numeral system continues to be widely used, however, in certain formal and minor contexts, such as on clock faces, coins, in the year of construction on cornerstone inscriptions, and in generational suffixes (such as Louis XIV or William Howard Taft IV). Romance languages (and also other languages such as Russian, Polish and Basque) write centuries in Roman numbers; in Spanish, for example, "21st century" is written "siglo XXI".
The Romans solidified the modern concept of the hour as one-24th part of a day and night. The English measurement system also retains features of the Ancient Roman foot (11.65 modern inches), which was used in England prior to the Anglo-Saxon settlement of Britain. The inch itself derives from the Roman , meaning one-twelfth part.
Three-age systems.
Although the present archaeological system of the three main ages—stone, bronze and iron—originates with the Danish archaeologist Christian Jürgensen Thomsen, the concept of dividing pre-historical ages into systems based on metals extends to Ancient Rome, originated by the Roman Lucretius in the first century BC.
Religion.
Christianity.
While classical Roman and Hellenistic religion were ultimately superseded by Christianity, many key theological ideas and questions that are characteristic of Western religions originated with pre-Christian theology. The first cause argument for the existence of God, for instance, originates with Plato. Design arguments, which were introduced by Socrates and Aristotle and remain widely discussed to this day, formed an influential component of Stoic theology well into the late Roman period. The problem of evil was widely discussed among ancient philosophers, including the Roman writers such as Cicero and Seneca, and many of the answers they provided were later absorbed into Christian theodicy. In Christian moral theology, moreover, the field of natural law ethics draws heavily on the tradition established by Aristotle, the Stoics, and especially by Cicero's popular Latin work, De Legibus. Cicero's conception of natural law "found its way to later centuries notably through the writings of Saint Isidore of Seville and the Decretum of Gratian" and influenced the discussion of the topic up through the era of the American Revolution.
Christianity itself also spread through the Roman Empire; since emperor Theodosius I (AD 379–395), the official state church of the Roman Empire was Christianity. Subsequently, former Roman territories became Christian states which exported their religion to other parts of the world, through colonization and missionaries.
Christianity also served as a conduit for preserving and transmitting Greco-Roman literary culture. Classical educational tradition in the liberal arts was preserved after the fall of the empire by the medieval Christian university. Education in the Middle Ages relied heavily on Greco-Roman books such as Euclid's "Elements" and the influential quadrivium textbooks written in Latin by the Roman statesman Boethius (AD 480–524).
Major works of Greek and Latin literature, moreover, were both read and written by Christians during the imperial era. Many of the most influential works of the early Christian tradition were written by Roman and Hellenized theologians who engaged heavily with the literary culture of the empire (see church fathers). St. Augustine's (AD 354–430) "City of God," for instance, draws extensively on Virgil, Cicero, Varro, Homer, Plato, and elements of Roman values and identity to criticize paganism and advocate for Christianity