The history of the Romanian language started in the Roman provinces north of the Jireček Line in Classical antiquity but there are 3 main hypotheses about its exact territory: the autochthony thesis (it developed in left-Danube Dacia only), the discontinuation thesis (it developed in right-Danube provinces only), and the "as-well-as" thesis that supports the language development on both sides of the Danube. Between the 6th and 8th century, following the accumulated tendencies inherited from the vernacular spoken in this large area and, to a much smaller degree, the influences from native dialects, and in the context of a lessened power of the Roman central authority the language evolved into Common Romanian. This proto-language then came into close contact with the Slavic languages and subsequently divided into Aromanian, Megleno-Romanian, Istro-Romanian, and Daco-Romanian. Due to limited attestation between the 6th and 16th century, entire stages from its history are re-constructed by researchers, often with proposed relative chronologies and loose limits.

From the 12th or 13th century, official documents and religious texts were written in Old Church Slavonic, a language that had a similar role to Medieval Latin in Western Europe. The oldest dated text in Romanian is a letter written in 1521 with Cyrillic letters, and until late 18th century, including during the development of printing, the same alphabet was used. The period after 1780, starting with the writing of its first grammar books, represents the modern age of the language, during which time the Latin alphabet became official, the literary language was standardized, and a large number of words from Modern Latin and other Romance languages entered the lexis.

In the process of language evolution from fewer than 2500 attested words from Late Antiquity to a lexicon of over 150,000 words in its contemporary form, Romanian showed a high degree of lexical permeability, reflecting contact with Thraco-Dacian, Slavic languages (including Old Slavic, Serbian, Bulgarian, Ukrainian, and Russian), Greek, Hungarian, German, Turkish, and to languages that served as cultural models during and after the Age of Enlightenment, in particular French. This lexical permeability is continuing today with the introduction of English words.

Yet while the overall lexis was enriched with foreign words and internal constructs, in accordance with the history and development of the society and the diversification in semantic fields, the fundamental lexicon—the core vocabulary used in everyday conversation—remains governed by inherited elements from the Latin spoken in the Roman provinces bordering Danube, without which no coherent sentence can be made.

Romanian descended from the Vulgar Latin spoken in the Roman provinces of Southeastern Europe north of the Jireček Line (a hypothetical boundary between the dominance of Latin and Greek influences).

Most scholars agree that two major dialects developed from Common Romanian by the 10th century. Daco-Romanian (the official language of Romania and Moldova) and Istro-Romanian (a language spoken by no more than 2,000 people in Istria) descended from the northern dialect. Two other languages, Aromanian and Megleno-Romanian, developed from the southern version of Common Romanian. These two languages are now spoken in lands to the south of the Jireček Line.

Of the features that individualize Common Romanian, inherited from Latin or subsequently developed, of particular importance are:
• appearance of the ă vowel;
• growth of the plural inflectional ending -uri for the neuter gender;
• analytic present conditional (ex: Daco-Romanian aș cânta);
• analytic future with an auxiliary derived from Latin volo (ex: Aromanian va s-cântu);
• enclisis of the definite article (ex. Istro-Romanian câre – cârele);
• nominal declension with two case forms in the singular feminine.
The use of the denomination Romanian (română) for the language and use of the demonym Romanians (Români) for speakers of this language predates the foundation of the modern Romanian state. Romanians always used the general term rumân/român or regional terms like ardeleni (or ungureni), moldoveni or munteni to designate themselves. Both the name of rumână or rumâniască for the Romanian language and the self-designation rumân/român are attested as early as the 16th century, by various foreign travelers into the Carpathian Romance-speaking space, as well as in other historical documents written in Romanian at that time such as Cronicile Țării Moldovei [ro] (The Chronicles of the land of Moldova) by Grigore Ureche.

The few allusions to the use of Romanian in writing as well as common words, anthroponyms, and toponyms preserved in the Old Church Slavonic religious writings and chancellery documents, attested prior to the 16th century, along with the analysis of graphemes show that the writing of Romanian with the Cyrillic alphabet started in the second half of the 15th century.

The oldest extant document in Romanian precisely dated is

Read more on Wikipedia

Romanian is a Romance language, belonging to the Italic branch of the Indo-European language family, having much in common with languages such as Italian, Spanish, French and Portuguese.

Compared with the other Romance languages, the closest relative of Romanian is Italian. Romanian has had a greater share of foreign influence than some other Romance languages such as Italian in terms of vocabulary and other aspects. A 1949 study by the Italian-American linguist Mario Pei, analyzing the degree to which seven Romance languages diverged from Vulgar Latin with respect to their accent vocalization, yielded the following measurements of divergence (with higher percentages indicating greater divergence from the stressed vowels of Vulgar Latin):
• Sardinian: 8%
• Italian: 12%
• Spanish: 20%
• Romanian: 23.5%
• Occitan: 25%
• Portuguese: 31%
• French: 44%
The study emphasized, however, that it represented only "a very elementary, incomplete and tentative demonstration" of how statistical methods could measure linguistic change, assigned "frankly arbitrary" point values to various types of change, and did not compare languages in the sample with respect to any characteristics or forms of divergence other than stressed vowels, among other caveats.

The lexical similarity of Romanian with Italian has been estimated at 77%, followed by French at 75%, Sardinian 74%, Catalan 73%, Portuguese and Rhaeto-Romance 72%, Spanish 71%.

The Romanian vocabulary became predominantly influenced by French and, to a lesser extent, Italian in the nineteenth and early twentieth centuries.
While most of Romanian grammar and morphology are based on Latin, there are some features that are shared only with other languages of the Balkans and not found in other Romance languages. The shared features of Romanian and the other languages of the Balkan language area (Bulgarian, Macedonian, Albanian, Greek, and Serbo-Croatian) include a suffixed definite article, the syncretism of genitive and dative case and the formation of the future and the alternation of infinitive with subjunctive constructions. According to a well-established scholarly theory, most Balkanisms could be traced back to the development of the Balkan Romance languages; these featur…

Read more on Wikipedia