Slavic AdstratumSee also: Adstratum, Early Slavs, and Proto-Slavic
Huge territories to the north of the Lower Danube were dominated by Goths and Gepids for at least 300 years from the 270s, but no Romanian words of East Germanic origin have so far been detected. On the other hand, Slavic influence on Romanian was much stronger than Germanic impact on French, Italian, Spanish and other Western Romance languages. Although "a number of Slavic loanwords have fallen victim to a strong re-latinisation process since the 19th century", the proportion of Slavic loanwords is still around 15%. The ratio of Slavic loanwords is especially high in the semantic fields of house (26,5%), religion and belief (25%), basic actions and technology (22,6%), social and political relations (22,5%), and agriculture and vegetation (22,5%). About 20% of the Romanian adverbs, nearly 17% of the nouns, and around 14% of the verbs are of Slavic origin. Slavic loanwords often coexist with a synonym inherited from Latin which sometimes give rise to semantic differentiation. For instance, both inherited "timp" and the Slavic loanword "vreme" may refer to either time or weather, but nowadays "vreme" is preferred in meteorological context. Loanwords borrowed from Slavic often have an emotional context, and they represent a positive connotation in many cases. Many linguists – including Günther Reichenkron and Robert A. Hall – argue that these features of the Slavic loanwords point at the one-time existence of bilingual communities with many Slavic speakers adopting Romanian, but their view have not been universally accepted.
The earliest stratum of Slavic loanwords – which is now represented by around 80 terms – was adopted in the Common Slavic period which ended around 850. However, the majority of Romanian words of Slavic origin was only adopted after the metathesis of the Common Slavic *tort-formula – which was "a specific type of syllable whereby t stands for any consonant, o for either e or o, and r for both r and l" – had been completed. Old Church Slavonic terms also enriched the Romanians' religious vocabulary in this period. Proto-Romanian even adopted words of Latin or Greek origin through Slavic mediation in this period. The bulk of the Old Church Slavonic loanwords has been preserved by all Eastern Romance variants which implies that their disintegration into separate languages did not start before 900. Each Eastern Romance variants and dialects adopted loanwords from the neighboring Slavic peoples thereafter. For instance, Ukrainian had an impact on the northern dialects of Daco-Romanian, while Croatian influenced Istro-Romanian.
In addition to vocabulary, Slavic languages also had effects on Eastern Romance phonology and morphology, although their extent is debated by specialists. The iotation of e in word-initial position in some basic words – that is the appearance of a semi vowel j before e in these terms – is one of the Romanian phonological features with a debated origin. Peter R. Petrucci argues that it was the consequence of a language shift from Common Slavic to Eastern Romance, while Grigore Nandriş emphasizes that "Latin e was diphthongised at an early period not only in" Romanian "but also in most Romance languages". The formation of numerals between eleven and nineteen clearly follow Slavic pattern – for instance, unsprezece ("one-on-ten"), doisprezece ("two-on-ten"), and nouăsprezece ("nine-on-ten") – which also indicates that a significant number of originally Slavic-speaking people once adopted Romanian.